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UBC Theses and Dissertations

The action of light and temperature on the activity of Simocephalus serrulatus (Koch) Alderdice, Donald Francis 1948

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^ JB 7 Ct>/a, J THE ACTION OF LIGHT AND TEMPERATURE ON THE ACTIVITY OF SIMOCEBHALUS SERRULATUS ( K O C H ) ^ ^ H 1 - by -Donald F r a n c i s A l d e r d i c e A T h e s i s Submitted i n P a r t i a l F u l f i l m e n t o f the Requirements f o r the Degree o f Master of A r t s i n the Department o f Zoology The U n i v e r s i t y o f B r i t i s h Columbia September, 194-8. TABLE OF CONTENTS Page A b s t r a c t . . I I n t r o d u c t i o n • I l l Acknowledgements XI Apparatus 1 I n t r o d u c t o r y Statement • 1 D e t a i l e d C o n s i d e r a t i o n 1 Temperature 1 L i g h t 9 M a t e r i a l s and Methods 17 Experimental Animals . . . . 17 C u l t u r e Methods 17 Procedure 19 P r e l i m i n a r y Experiments . 23 C h a r a c t e r i s t i c s o f Water Media 23 R e v e r s a l o f P h o t o t a c t i c S i g n 24 Method f o r Treatment o f Data 26 Exp e r i m e n t a l R e s u l t s 29 Temperature Preferendum 29 Random D i s t r i b u t i o n 32 G r a d i e n t s o f L i g h t I n t e n s i t y 34 P r e a d a p t a t i o n to L i g h t I n t e n s i t y . . . . . . . . 42 U l t r a - v i o l e t l i g h t 44 Wave-length o f V i s i b l e L i g h t . . . 45 S p e c t r a l Regions o f Graded I n t e n s i t y 47 Combined L i g h t and Temperature G r a d i e n t s w i t h Wave-length V a r i a t i o n s 50 Page D i s c u s s i o n . . . . . 58 Temperature Preferendum . 58 Response to G r a d i e n t s of L i g h t I n t e n s i t y . . . . 60 I n f l u e n c e o f I n t e n s i t y L e v e l 60 Rate o f R i s e o f I n t e n s i t y i n a G r a d i e n t . . . 62 D u r a t i o n o f S t i m u l a t i o n 64 I n f l u e n c e o f P r e a d a p t a t i o n to L i g h t on Response . 67 A c t i o n o f U l t r a - v i o l e t L i g h t . 68 I n f l u e n c e o f Wave-length on Response to V i s i b l e L i g h t 69 R e a c t i o n s to G r a d i e n t s o f I n t e n s i t y o f S p e c i f i c Wave-length Regions 71 Response to Combined L i g h t and Temperature G r a d i e n t s • 73 C o n c l u s i o n s 78 Summary • 82 Appendix 85 L i t e r a t u r e C i t e d • 113 I ABSTRACT designed and Apparatus has been A developed f o r d e t e r m i n i n g the r e -th» plankton C«u«ta.*«ar» sponse o f 'S imocephalus s e r r u l a t u s (Koch) to h o r i z o n t a l g r a d -i e n t s o f l i g h t and temperature . These f a c t o r s were v a r i e d i n d e p e n d e n t l y or combined under s t a n d a r d i z e d c o n d i t i o n s . The temperature preferendum f o r t h i s organism, c u l t u r e d i n a c o n -s t a n t environment , was found t o be 19.13°C, f o r animals p r e -v i o u s l y h e l d at 19°C. f o r 14 h o u r s . The steepness o f a tem-p e r a t u r e g r a d i e n t was shown to i n f l u e n c e the r a t e o f aggre-g a t i o n a t a preferendum temperature . A t a constant tempera-t u r e ( temperature preferendum) r e a c t i o n s to l i g h t were then s t u d i e d . L i g h t i n t e n s i t y , g r a d i e n t s o f l i g h t i n t e n s i t y , l i g h t q u a l i t y , and g r a d i e n t s o f l i g h t q u a l i t y were c o n s i d e r e d . Animals were p o s i t i v e l y p h o t o t a c t i c to the range o f v i s i b l e l i g h t i n t e n s i t i e s c o n s i d e r e d , but became i n d i f f e r e n t to l i g h t on the a d d i t i o n o f chemica l substances t o the water medium. An a b s o l u t e optimum l i g h t i n t e n s i t y was demonstrated, a t which the response to l i g h t i s g r e a t e s t i n magnitude. The r a t e o f r i s e o f l i g h t i n t e n s i t y was shown to be d i r e c t l y r e l a t e d t o the magnitude o f the response and i n d i r e c t l y r e l a t e d to the time f o r the response t o r e a c h a peak* up to the a b s o l u t e optimum l i g h t i n t e n s i t y . The i n t e n s i t y of i l l u m i n a t i o n was **' i n v e r s e l y r e l a t e d t o the time f o r a d a p t a t i o n to o c c u r . The magnitude o f the l i g h t response was i n v e r s e l y r e l a t e d t o the i n t e n s i t y o f a p r e - a d a p t a t i o n l i g h t s t i m u l u s . Wave l e n g t h s o i n the r e g i o n o f 3000 to 3500 A , w i t h a mean v a l u e o f I I o approx imate ly 3300 A,were shown t o r e v e r s e the p r i m a r y s i g n o f the p h o t o t a c t i c response . The s p e c t r a l s e n s i t i v i t y / c u r v e f o r the p o s i t i v e p h o t o t a c t i c response to v i s i b l e l i g h t e x -. o tended from 4000 to 6400 A . F i n a l l y , l i g h t f a c t o r s were a p p l i e d to the animals i n a temperature g r a d i e n t and q u a n t i -t a t i v e d a t a on the response o b t a i n e d . The i n t e r a c t i o n o f the two f a c t o r s produced a response w h i c h i s the r e s u l t a n t of the f a c t o r s a c t i n g i n o p p o s i t i o n . I l l INTRODUCTION The study of the a c t i o n o f envi ronmenta l f a c t o r s , w h i c h govern or e x e r t a c o n t r o l l i n g i n f l u e n c e on the a n i m a l , has been approached i n two d i f f e r e n t manners. The f i r s t method r e q u i r e d o b s e r v a t i o n s on the p o p u l a t i o n under n a t u r a l c o n d i -t i o n s . The response o f the p o p u l a t i o n i s then c o r r e l a t e d w i t h c o e x i s t i n g environmenta l c o n d i t i o n s and p o s s i b l e i n t e r -r e l a t i o n s are I n f e r r e d . The behaviour o f the p o p u l a t i o n i s then r e f e r r e d t o as t h a t of the i n d i v i d u a l . Work o f t h i s c h a r a c t e r has been r e p o r t e d by many a u t h o r s . The second method o f approach i s t h a t by which the envi ronmenta l f a c t o r s t o be s t u d i e d are c o n s t r u c t e d e x p e r i m e n t a l l y t o s i m u l a t e n a t -u r a l c o n d i t i o n s . The a c t i o n o f any f a c t o r i s then determined as the response o f a s i n g l e i n d i v i d u a l or o f a sample o f the p o p u l a t i o n . More r e c e n t s t u d i e s tend t o . f a l l i n t o t h i s c l a s s . I t i s proposed to f o l l o w the l a t t e r approach i n a s tudy ' the. Ci-ustocean P/anKtet-of Simocephalus s e r r u l a t u s (Koch) to o b t a i n i n f o r m a t i o n o f a nature t h a t w i l l e v e n t u a l l y answer the q u e s t i o n o f why, as w e l l as how such responses o c c u r . Temperature, one o f the most important f a c t o r s e x i s t i n g i n the a q u a t i c environment , ac t s upon the p h y s i o l o g i c a l p r o -cesses o f c o l d - b l o o d e d i n v e r t e b r a t e s by i n f l u e n c i n g the meta-b o l i c r a t e and the r e p r o d u c t i v e c y c l e . MacArthur and B a i l l i e (1929 a,b) have shown t h a t the l i f e c y c l e o f Daphnia magna i s pro longed and the r e p r o d u c t i v e r a t e i s lengthened by a IV decrease i n temperature . The e f f e c t s would be dependent on ii the s l o w i n g o f the m e t a b o l i c r a t e which would a l s o govern the a c t i v i t y o f the a n i m a l . Brown (1929) has p o i n t e d out t h a t the d i s t r i b u t i o n o f the C l a d o c e r a i s i n f l u e n c e d by g e o g r a p h i c a l d i f f e r e n c e s i n environmenta l temperatures . Temperature a l s o i n d i r e c t l y c o n t r o l s o ther n a t u r a l f a c t o r s such as gas c o n -c e n t r a t i o n i n s o l u t i o n , v i s c o s i t y o f water and water d e n s i t y . C l a r k e (1932) has demonstrated t h a t a r e v e r s a l o f p h o t o t r o p i c response occurs f o r Daphnia when the water i s heated or c o o l e d r a p i d l y . Eyden (1923) has shown t h a t the s p e c i f i c g r a v i t y o f x Daphnia , through i t s normal v a r i a t i o n s , can e x e r t a change i n the v e r t i c a l d i s t r i b u t i o n o f the a n i m a l s . I t i s g e n e r a l l y s t a t e d t h a t there are three fundamental temperature l e v e l s w i t h i n the l i m i t s o f an a n i m a l * s normal t o l e r a n c e : the maximum, the minimum and the optimum tempera-t u r e . The former two are the l i m i t s o f thermal t o l e r a n c e . The optimum temperature i s d i f f i c u l t to d e f i n e . Fry , (194?) s t a t e s , " t h e term optimum may be u s e d . . . a s d e s c r i b i n g a l e v e l o f a c o n t r o l l i n g f a c t o r a t which a g i v e n a c t i v i t y . . . c a n be best c a r r i e d o n , " b e s t " [meaning accomplishment] a t the h i g h -es t l e v e l o f the measurement t a k e n . " However, a l l three tem-p e r a t u r e l e v e l s are not constant f o r a s p e c i e s , there b e i n g d i f f e r e n c e s w i t h age o f the i n d i v i d u a l , p e r i o d o f the l i f e c y c l e , and the temperature to which the animal was p r e v i o u s l y adapted. F r y (1947) and B r e t t (1944) d i s c u s s the a c t i o n o f temperature a c c l i m a t i o n and show the r e l a t i o n s h i p o f t h i s V preadaptation to the ab i l i t y of the animal to withstand max-imum and minimum.temperatures. The temperature preferendum, that temperature in which animals w i l l aggregate in a grad-ient (Fraenkel and Gunn, 1940) Is also influenced by acclim-ation. As the acclimation temperature increases, so w i l l the temperature preferendum increase (Fry, 1947). Light may be considered a significant environmental factor from i t s effects on the behaviour of aquatic animals. Of the phenomena which appear to be related to light, diurnal migrations of members of the marine and fresh-water plankton populations are most striking. These reactions vary in range of movement and time of occurrence from species to species. Various characteristics of the fundamental reactions to light have been compiled by Rose (1929) for numerous species. Clarke (1932) states that the primary sign of phototropism in Daphnia i s not altered by the absolute intensity of the light . It i s however, effected by age of the individual, water temperature, and conditions existing i n a culture medium. He also states that a reversal of the phototropic sign can be demonstrated for differences in light intensity only when the rate and magnitude of the intensity change reaches a threshold value. Johnson (1938) found that Acartia clausi moved toward a source of light after a previous sojourn i n darkness while the opposite response occurred for those held in light pre--vious to experimentation. Johnson and Raymont (1939) demon-strated that Centropages typicus i s primarily positively V I p h o t o t r o p i c to a l l l i g h t i n t e n s i t i e s and t h a t i t remains so a f t e r cons tant exposure t o a l l i n t e n s i t i e s below t h a t o f b r i g h t s u n l i g h t . The lowest i n t e n s i t y which would e l i c i t a response was approx imate ly .005 f o o t - c a n d l e s . Daphnia p u l e x were shown by D i c e (1914) to be p o s i t i v e l y p h o t o t r o p i c to weak l i g h t at 20°C. and to be i n d i f f e r e n t to l i g h t i n t e n s i -t i e s s t ronger than weak d i f f u s e d a y l i g h t . He a l s o found the p o s i t i v e response i n c r e a s e d w i t h decreases I n temperature b e -low 2 0 ° C , w h i l e the oppos i te r e a c t i o n o c c u r r e d i f the tem-pera ture was r a i s e d above 20°C. D i c e concludes t h a t d i u r n a l m i g r a t i o n s o f Daphnia are caused c h i e f l y by v a r i a t i o n s i n the g e o t a c t i c response induced by changes i n l i g h t i n t e n s i t y ( i t a l i c s m i n e ) . He reasoned t h a t seasonal changes I n v e r t i -c a l d i s t r i b u t i o n are l a r g e l y governed by changes i n g e o t a x i s induced by seasonal temperature changes. Spooner (1933) has demonstrated f o r a number of marine ar thropods t h a t d i r e c t i o n of l i g h t i s the pr imary m o t i v a t i n g f o r c e i n l i g h t movements and t h a t i t a c t s i r r e s p e c t i v e o f accompanying i n -t e n s i t y changes. Moore (1912) has shown t h a t the p h o t o t r o p i c response o f Daphnia r e v e r s e s i n wavelengths below 3341 A*. From t h i s d i s c u s s i o n i t can be seen t h a t the response to one f a c t o r under c o n t r o l l e d c o n d i t i o n s may v a r y f rom spec ies to s p e c i e s . The p o t e n t i a l i n t e r r e l a t i o n s o f the v a r i o u s aspedts o f each f a c t o r present a wide range over w h i c h the v a l u e o f the response may v a r y . The author c o n s i d -e r s t h a t when the c h a r a c t e r i s t i c s o f the i s o l a t e d response t o V I I each f a c t o r are known, and t h a t when these c h a r a c t e r i s t i c s are then i n t e g r a t e d , the p r e s e n t mass o f seemingly u n r e l a t e d i n f o r m a t i o n w i l l show d e f i n i t e p a t t e r n s . The study was designed to permit an experimental a n a l y -s i s o f the r e a c t i o n s o f animals to environmental f a c t o r s con-t r o l l e d so t h a t the d a t a c o u l d be t r e a t e d s t a t i s t i c a l l y . T h i s statement forms the f o u n d a t i o n upon which the problem was arranged. The two f a c t o r s c o n s i d e r e d were l i g h t and temperature. The method p e r m i t t e d each f a c t o r to be i s o l a t e d . The e f f e c t s o f any aspect o f one f a c t o r on the a c t i v i t y o f the animal c o u l d be c o n s i d e r e d s i n g l y , o r , v a r i o u s aspects o f each o f the two f a c t o r s c o u l d be combined to determine the i n f l u e n c e of a combination o f f a c t o r s on a c t i v i t y . The f o l l o w i n g p o s s i b l e c o n s i d e r a t i o n s i n t h i s r e s p e c t are reviewed. I TEMPFJIATURE 1. Constant Values a) a c t i v i t y a t constant temperatures throughout the animals range o f thermal t o l e r a n c e . b) l e t h a l l i m i t s o f animals a c c l i m a t e d to temper-at u r e s w i t h i n the range o f thermal t o l e r a n c e . c) r a t e s o f a c c l i m a t i o n to temperature l e v e l s w i t h i n the range of thermal t o l e r a n c e . VIII 2 . Gradients a) the preferendum temperature* b) the e f f e c t of temperature acclimation on the temperature preferendum. c) differences i n rates of gain of heat and cold tolerance. d) rate of response to the steepness of a temper-ature gradient. II LIGHT 1 . Intensity a) rate of response to a gradient of i n t e n s i t y . b) e f f e c t of duration of the stimulus. c) response to i n t e n s i t y l e v e l s . d) response to the gradient, duration and l e v e l of in t e n s i t y when previously acclimated to an in t e n s i t y l e v e l . 2 . Quality a) a c t i v i t y at wave-lengths through the v i s i b l e spectrum with radiant f l u x as a v a r i a b l e . b) a c t i v i t y i n an i n t e n s i t y gradient of portions of the v i s i b l e spectrum. c) a c t i v i t y i n a portion of the v i s i b l e spectrum as a gradient at other l e v e l s of i n t e n s i t y . III TEMPERATURE AND LIGHT a) a c t i v i t y i n a temperature gradient when i n -fluenced by a gradient of portions of the v i s -i b l e spectrum. IX b) a c t i v i t y i n a temperature g r a d i e n t when i n -f l u e n c e d by a g r a d i e n t o f each o f the p o r t i o n s a t v a r i o u s i n t e n s i t y l e v e l s . c) d u r a t i o n o f s t i m u l u s as e f f e c t i n g a c t i v i t y at each i n t e n s i t y f o r a g i v e n p o r t i o n o f the v i s i b l e spectrum. d) d u r a t i o n of stimulus as e f f e c t i n g a c t i v i t y at each p o r t i o n o f the v i s i b l e spectrum. The p a r t i c u l a r a s p e c t s which have been c o n s i d e r e d are o u t l i n e d i n the Procedure. B e f o r e proceeding f u r t h e r i t i s necessary to d e f i n e the terms used i n r e f e r r i n g t o the p h o t i c response. The term "phototropism" has been used here to d e s c r i b e a r e a c t i o n t o l i g h t where the word appears i n the study of an author r e -f e r r e d t o . T h i s term has g r a d u a l l y been r e s t r i c t e d i n usage to d e s c r i b e the l i g h t r e a c t i o n s o f p l a n t s and s e s s i l e animals. The term " p h o t o t a x i s " i s c o n s i d e r e d by F r a e n k e l and Gunn 0194O) as a r e a c t i o n to l i g h t i n which the body o f the a n i -mal i s o r i e n t e d i n l i n e w i t h the source o f i l l u m i n a t i o n . These authors d e s c r i b e the p h o t i c response of Daphnia as a ' d o r s a l l i g h t r e a c t i o n ' , and d e f i n e i t thus: " o r i e n t a t i o n so t h a t l i g h t i s kept p e r p e n d i c u l a r to both l o n g and t r a n s -v e r s e axes o f the body; u s u a l l y d o r s a l , but i n some animals v e n t r a l . Locomotion need not occur." The ' d o r s a l l i g h t r e -a c t i o n ' i s - i n c l u d e d i n a c a t e g o r y termed ' t r a n s v e r s e o r i e n t -a t i o n s ' i n which o r i e n t a t i o n i s a t a 'temporary f i x e d angle X to the d i r e c t i o n o f the e x t e r n a l s t i m u l u s . * I n the present s t u d y , the term p h o t o t a x i s i s used t o d e s c r i b e the p h o t i c response and i s d e f i n e d i n the g e n e r a l sense of the word as " a d i r e c t e d r e a c t i o n to l i g h t a c t i n g as a s t i m u l u s . 1 1 » The author wishes to express h i s g r a t e f u l a p -p r e c i a t i o n to D r . W.A. Clemens, Head o f the Zoology-Department, and to D r . W.S. H o a r , P r o f e s s o r o f Z o * -o l o g y and F i s h e r i e s ^ - who s u p e r v i s e d the work, f o r w i l l i n g a s s i s t a n c e , c r i t i c i s m of the f i n a l paper and f o r the e f f o r t s undertaken to p r o v i d e the equipment. The author i s i n d e b t e d to D r . V . C . B r i n k , Department o f Agronomy, and M r . D . G . Chapman , Department o f Mathemat ics , f o r a s s i s t a n c e i n the development and i n t e r p r e t a t i o n o f s t a t i s t i c a l p r o c e d u r e s . i V a l u a b l e a s s i s t a n c e has been r e c e i v e d from D r . A . M . C r o o k e r , Department o f P h y s i c s , through the l o a n o f e l e c t r i c a l equipment and by h i s i n -t e r p r e t a t i o n o f e l e c t r i c a l and o p t i c a l problems connected w i t h the s t u d y . Thanks are extended to those f e l l o w s tudents who a t numerous t imes a s s i s t e d i n the c a r r y i n g out of the e x p e r i m e n t a l p r o c e d u r e , and to Miss M. Merry B.A.,who devoted c o n s i d e r a b l e time a s s i s t i n g i n the p r e p a r a t i o n o f the f i n a l . d r a f t . APPARATUS 1 . In developing the apparatus i t was necessary to incor-porate features which would permit: a) The analysis of var i a t i o n s i n a c t i v i t y by d i r e c t counts of the animals. b) The analysis of the i n t e r a c t i o n of facto r s by a progressive elimination of each v a r i a b l e . c) The elimination of the e f f e c t s of gravity i n deter-mining the d i s t r i b u t i o n of the animals under the Influence of an external stimulus such as l i g h t or temperature l e v e l . INTRODUCTORY STATEMENT The. experimental apparatus (was set up i n a darkroom. The darkroom housed a cold temperature tank, the inner dimen-sions being\ two feet wide by four feet long and three feet deep. This tank contained the c i r c u l a t i o n r e s t r i c t e r trough. Set i n the l a t t e r trough was the temperature regulator trough which i n turn contained the innermost experimental trough* The three inner troughs are i l l u s t r a t e d i n t h e i r r e l a t i v e positions i n Figure 3 j t h e i r dimensions are shown i n Figure 1. DETAILED CONSIDERATION Temperature, 1. Gradients. To set up a temperature gradient i t i s necessary to balance the rate of heat outflow against the 2 F i g u r e 1. Temperature apparatus. Trough dimensions. TEMPERATURE APPARATUS T R O U G H D I M E N S I O N S I. C I R C U L A T I O N RESTRICTOR 2. T E M P E R A T U R E R E G U L A T O R IQ.2 -36- ft6.2 IS. I 3. E X P E R I M E N T A L T R O U G H h 36-:i2-3. F i g u r e 2. Temperature apparatus. D e t a i l s o f troughs. T E M P E R A T U R E A P P A R A T U S D E T A I L S OF TROUGHS I. COMPARTMENT h—& • L +—2t-BAFFLE J ©,R=5'i"~ 2.THERMOREGULATOR RAMP r ISOMETRIC VIEW • SOLDERED TO TROUGH 2 (FIG.3> 3 EXPERIMENTAL TROUGH C/S r- 2"——i 4.SECONDARY COMPARTMENT BAFFLE _ SUPPORTING LIP life—-tr—2"—•/• i/,' 5.COMPARTMENT BAFFLE HOUSING ^ -SOLDERED TO INNER WALL OF TROUGH 2-F i g u r e 3» Temperature apparatus. Assembled i s o m e t r i c view. T E M P E R A T U R E A P P A R A T U S r a t e o f heat i n f l o w . To m a i n t a i n the g r a d i e n t i n a h o r i z o n -t a l plane there must he no v e r t i c a l s t r a t i f i c a t i o n o f the water. The tendency of the water to f l o w by c o n v e c t i o n be-tween two connected areas having d i f f e r e n c e s i n temperature l e v e l ^ must be overcome. The heat input'was maintained by 300 watt L o l a g immer-s i o n h e a t e r s used i n c o n j u n c t i o n w i t h Fenwal s e n s i -t i v i t y b i m e t a l thermoregulators ( F i g . 3 ) . The heat o u t f l o w was maintained by the c o l d temperature tank which c o u l d be a d j u s t e d to c o n t r o l the temperature around the apparatus w i t h -i n a 0°C. to 20°C. range. The c o n t r o l was accomplished by a r e f r i g e r a t i n g u n i t working i n c o n j u n c t i o n with a thermo-r e g u l a t o r o f i 0.5°C. s e n s i t i v i t y . Thorough mixing o f the c o l d temperature tank water was assured by the a c t i o n o f a stream o f compressed a i r . By adjustment o f the c o l d temper-ature tank thermoregulator and those o f the temperature r e -g u l a t o r t r o u g h ( F i g . 3)» any temperature l e v e l c o u l d be main-t a i n e d i n d e f i n i t e l y . The temperature r e g u l a t o r trough (Trough 2, F i g . 3) was c l o s e d a t both ends and open on top. For o b t a i n i n g a temperature g r a d i e n t i n the temperature r e g u l a t o r t r o u g h and consequently the same g r a d i e n t i n the experimental trough (Trough 3» F i g . 3)> the former was d i v i d e d i n t o compartments by compartment b a f f l e s ( F i g s . 3 , 2(])). C i r c u l a t i o n by con-v e c t i o n c u r r e n t s w i t h i n t h i s trough was then broken i n t o a number of s m a l l u n i t s . By the s e t t i n g o f the temperature r e g u l a t o r trough immersion h e a t e r s at v a r i o u s temperature l e v e l s , a g r a d i e n t o f compartment temperatures c o u l d be e s -t a b l i s h e d from one end o f the trough to the o t h e r . The c i r c u l a t i o n r e s t r i c t o r t r o u g h (Trough 1 , F i g . 3) was designed t o separate the temperature r e g u l a t o r trough from complete exposure to the o u t s i d e tank temperature. The stream o f a i r bubbles, mentioned p r e v i o u s l y , was d i r e c t e d a g a i n s t the bottom o f the temperature r e g u l a t o r t r o u g h a t th a t end o f the c i r c u l a t i o n r e s t r i c t o r t rough open d i r e c t l y t o the tank temperature. T h i s procedure maintained the tem-p e r a t u r e s o f the temperature r e g u l a t o r trough and experiment-a l t r o u g h equal at one end to t h a t o f the c o l d temperature tank. Thus, the temperature o f the f i r s t compartment was e s t a b l i s h e d . As the o p p o s i t e end o f the c i r c u l a t i o n r e s t r i c -t o r trough was c l o s e d , c i r c u l a t i o n o f tank water d i r e c t l y be-neath the temperature r e g u l a t o r trough was i n h i b i t e d toward t h a t end. T h i s f e a t u r e produced a reduced heat o u t f l o w from the l a t t e r toward the c l o s e d end o f the former trough. By t h i s means, temperature f l u c t u a t i o n s i n the compartments at the warm end o f the g r a d i e n t wejre kept to a minimum. The experimental trough ( F i g s . 1 ( 3 ) , 3 ( 3 ) ) f i t t e d i n t o d e p r e s s i o n s i n the compartment b a f f l e s and was equal i n l e n g t h to the temperature r e g u l a t o r trough. The experimental trough c o n t a i n e d the experimental animals. "By v i r t u e o f the heat conducting q u a l i t i e s o f the copper sheet used i n the c o n s t r u c -t i o n o f the troughs, heat t r a n s f e r e n c e o c c u r r e d q u i c k l y and with a minimum o f l a g . The temperature o f the experimental trough water corresponded v e r y c l o s e l y t o t h a t o f the temper-ature r e g u l a t o r trough. Because o f the p l a c i n g o f numerous compartment b a f f l e s , heat t r a n s f e r e n c e between compartments was due t o t a l l y t o c o n d u c t i o n . Next, secondary compartment b a f f l e s ( F i g . 2(4) ) were hung, two to a compartment, from the experimental trough i n t o the water o f the temperature r e g u l a t o r trough ( F i g . 3)» t o break up c o n v e c t i o n c u r r e n t s w i t h i n each compartment. The f i n a l type o f g r a d i e n t e s t a b l i s h e d i s i l l u s t r a t e d i n F i g . 4 and c o n s i s t e d o f s h o r t jumps t o h i g h e r temperature l e v e l s , each s m a l l l e v e l b e i n g a g r a d i e n t i t s e l f . F i g u r e 4 . Example o f type o f g r a d i e n t e s t a b l i s h e d by apparatus. 1 . Temperature o f Temper-ature r e g u l a t o r trough. 2. Temperature of E x p e r i m e n t a l trough. 3» L i m i t s o f v a r i a t i o n o f E x p e r i m e n t a l trough temperature. 3 4 5 COMPORTMENT 8. The i n n e r s u r f a c e o f the experimental trough was t i n n e d to e l i m i n a t e the e f f e c t s o f t o x i c copper i o n s and coated w i t h lampblack melted i n t o p a r a f f i n wax. T h i s a f f o r d e d a non-r e f l e c t i n g s u r f a c e . F i l t e r e d pond water was the medium used i n the e x p e r i m e n tal trough. The depth o f water was l i m i t e d to one c e n t i m e t e r . With t h i s depth o f water no c o n v e c t i o n c u r r e n t s were s e t up between the two ends of the temperature g r a d i e n t . I t i s p o s s i b l e t h a t such c u r r e n t s were able to form, but as no f l o w was found to occur, i t i s thought t h a t the p r o x i m i t y o f the l i m i t e d amount o f water to the w a l l s o f the experimental trough must have a d j u s t e d the temperature d i f f e r e n c e s v e r y r a p i d l y . The apparatus was used t o m a i n t a i n g r a d i e n t s from approximately 4°C. t o 3&°C. 2. Constant Temperatures. To e s t a b l i s h a u n i f o r m tem-p e r a t u r e over the t o t a l l e n g t h o f the experimental trough, the compartment b a f f l e s and secondary compartment b a f f l e s c o u l d be removed. With a l l temperature r e g u l a t o r t r o u g h thermoregulators set t o equal h e a t i n g l e v e l s , and the water w i t h i n the trough c i r c u l a t e d by a i r i n l e t s , a constant u n i f o r m temperature c o u l d be maintained w i t h a h i g h degree o f a c c u r -acy. F o r t h i s procedure the tank temperature was a d j u s t e d t o a s l i g h t l y lower l e v e l (2 to 3 ° C ) , when o p e r a t i n g a t 2 0 ° C , to reduce the temperature overshoot i n the temperature r e -g u l a t o r trough to a minimum. The w i r i n g o f the thermoregula-t o r s and immersion h e a t e r s i s diagrammed i n F i g u r e 5. 9. F i g u r e 5. W i r i n g diagram o f thermoregulators and immersion h e a t e r s . * WIRING DIAGRAM OF IMMERSION HEATERS AND THERMOREGULATORS ? , * 1 i i r i 1 . j ' k r 1 • HEATERC300W) PILOT L I G H T - C O N T R O L IOA 120V LINE: . A C i i ( I 2 O 0 W ) L i g h t . 1. G r a d i e n t s . The p r i n c i p l e o f o b t a i n i n g a g r a d i e n t o f l i g h t i n t e n s i t y was s i m i l a r to th a t used by U l l y o t t (1936). I n the presen t study, the g r a d i e n t apparatus c o n s i s t e d o f a r e c t a n g l e ( F i g . 6(1), 7) o f g a l v a n i z e d i r o n , open on top and bottom and made to f i t the outer dimensions o f the temper-ature r e g u l a t o r trough. I t was h e l d i n pl a c e by short " l e g s " ( F i g . 6(4) ). L i g h t b a f f l e s o f the same m a t e r i a l ( F i g . 6(3), 7) were designed to s l i p between and be h e l d h b y the s i d e s o f the r e c t a n g l e ; the r e c t a n g l e was then d i v i d e d i n t o areas c o r r e s -ponding i n s i z e and p o s i t i o n to the compartments o f the tem-pera t u r e r e g u l a t o r trough. T h e r e f o r e , counts o f the animals 10 . F i g u r e 6. R a d i a t i o n apparatus. D e t a i l s of c o n s t r u c t i o n . RADIATION APPARATUS RECTANGLE TOP/BOTTOM OPEN -36" 3£E*T 4& 2.VIEW SCREEN -37*-END VIEW 2 3. LIGHT BAFFLE 2 S i <5 - 6 V -THICIVNESS OF MATERIAL USED 4. LEG SOLDERED TO BOTTOM ENDS OF I. 1 F i g u r e 7 . Complete apparatus assembled to show r e l a t i v e p o s i t i o n of a l l p a r t s . 12. i n the experimental trough immediately below the l i g h t b a f f l e s , c o u l d be made f o r ni n e a r b i t r a r y s e c t i o n s . The animals were s t i l l f r e e to move over the f u l l l e n g t h o f the experimental trough. A p i e c e o f d o u b l e - f l a s h e d white o p a l g l a s s was f i t t e d . over the top o f the r e c t a n g l e and l i g h t b a f f l e s ( F i g . 7) and p e r m i t t e d d i s p e r s i o n o f l i g h t v e r t i c a l l y , without i n t e r -f e r e n c e o f shadows c a s t by r e f l e c t i o n . A l l i n n e r s u r f a c e s of the apparatus were coated w i t h Kodak Kodacoat b l a c k p a i n t t o e l i m i n a t e r e f l e c t i n g s u r f a c e s . F i n a l l y , a viewing screen ( F i g . 6 ( 2 ) , 7) was s l i p p e d on/to the end f l a n g e s o f the r e c t a n g l e . The animals c o u l d be viewed through t h i s without i n t e r f e r i n g w i t h the l i g h t d i s -p e r s i o n o f the o p a l g l a s s . The scree n formed a s h i e l d so th a t no l i g h t f e l l on the experimental trough"other than t h a t e n t e r i n g by the o p a l g l a s s . 2 . I n t e n s i t y . G e n e r a l E l e c t r i c tungsten f i l a m e n t gas-f i l l e d lamps were used through t h i s s e c t i o n o f the study. By u s i n g v a r i o u s lamps, v a r y i n g the d i s t a n c e from and the angle o f the lamp to the apparatus, g r a d i e n t s o f v a r i o u s r a t e s o f r i s e and g r a d i e n t s at v a r i o u s i n t e n s i t y l e v e l s c o u l d be s e t up. Measurements o f l i g h t i n t e n s i t y were made w i t h a Weston P h o t r o n i c c e l l , model 594, type 1; v a r i a b l e r e s i s t o r (34A, 0 - 3 6 0 0 n ) ; and, depending on the i n t e n s i t y , e i t h e r a micro-ammeter or a galvanometer o f 0 .02 microamperes per m i l l i m e t e r 13. s e n s i t i v i t y . 3. Q u a l i t y . The i n f l u e n c e o f l i g h t q u a l i t y was d e t e r -mined w i t h the a i d o f a s e r i e s o f C o r n i n g short-wave c u t o f f f i l t e r s . ( T able I ) Table I . C h a r a c t e r i s t i c s o f the s h o r t wave c u t o f f f i l t e r s . V a l u e s are rounded o f f . 3400 A i s the lower l i m i t o f t r a n s m i s s i o n o f the o p a l g l a s s . Region S e l e c t i v e l y C o rning G l a s s 50% C u t o f f L e v e l Omitted i n Apparatus No. (Angstrom U n i t s ) (Angstrom U n i t s ) 3850 3900 3400-3900 3387 4600 3400-4600 3384 5100 3400-5100 3482 5600 3400-5600 2424 5900 3400-5900 2408 6300 3400-6300 2540 10000 3400-10000 Keeping i n t e n s i t y c o n s t a n t , the r e l a t i v e r a d i a n t f l u x w i t h i n s u c c e s s i v e l y r e s t r i c t e d p o r t i o n s o f the v i s i b l e spec-trum (Table I) was measured. The measurements were made with the P h o t r o n i c c e l l a f t e r c o r r e c t i n g f o r the c e l l ' s spec-t r a l s e n s i t i v i t y . By p l o t t i n g the average response o f the c e l l t o the s p e c t r a l r e g i o n s c o n s i d e r e d , the r e l a t i v e r a d i a n t f l u x , based on t h a t t r a n s m i t t e d by the o p a l g l a s s as 100 p e r -cent, c o u l d then be found ( F i g . 8). I n d e s i g n i n g the apparatus, u s e f u l i n f o r m a t i o n has been gained from pamphlets i s s u e d by the American Instrument 14. Company, Canadian- General E l e c t r i c Company L i m i t e d , Weston E l e c t r i c a l Instrument C o r p o r a t i o n and Corning G l a s s Works. F i g u r e 8 . Graph o f the r e l a t i v e r a d i a n t f l u x as a f u n c -t i o n o f wave-length. V a l u e s are based on the t r a n s m i s s i o n o o f the o p a l g l a s s as 100 pe r c e n t and determined by the use o f the f i l t e r s l i s t e d i n T a b l e I . 3400 4000 SOOO 6000 7000 WfWe-ieNQTH (H/XXTltOMS) The f i l t e r s were mounted over openings c u t i n b l a c k opaque paper so t h a t each f i l t e r was c e n t r e d over one compartment. In t h i s manner, s e l e c t e d p o r t i o n s o f the spectrum c o u l d be omitted over the l e n g t h o f the trough at one time. Lamps were arranged over the f i l t e r s at a d i s t a n c e p r o v i d i n g equal luminous f l u x f o r each compartment. A study o f the response o f the animals t o a g r a d i e n t o f i n t e n s i t y was made f o r each o f the s p e c t r a l r e g i o n s con-s i d e r e d . The i l l u m i n a t i n g lamp was e n c l o s e d i n a b l a c k box, 15. open at one end. The f i l t e r used was slipped into this open end and the box set up at one end of the apparatus. By adjust-ing the position of the lamp, gradients of equal intensity for each f i l t e r could be constructed. A quartz lamp generating into the short blue wave-length region and having a peak transmission at 2536 % was used to find the effects of ultra-violet l i g h t . Figures 9 to 13 show a breakdown assemblage of the tem-perature and radiation apparatus. Photographs to il l u s t r a t e the installation of the troughs. Figure 9 . Tank with circulation restrictor trough in place. F i g u r e 10. The t e m p e r a t u r e r e g u l a t o r t r o u p h has been added. Figure 13. Complete apparatus assembled. MATERIALS AND METHODS Experimental Animals Simocephalus serrulatus (Koch) was used throughout the study. Only adult females were used. The species resembles Daphnia morphologically, and i s of the same family, Daphnidae. Culture Methods The animals were obtained in September, 1947 > i n Deer Lake, Burnaby, B.C. They were caught with a No. 20 bolting s i l k plankton net. Cultures of the animals were maintained in the following manner. Water from the University Botanical Garden pond was obtained and f i l t e r e d . After the water had been standing several days, approximately one-half ounce of dried sheep manure was suspended in a glass wool bag i n 14 l i t r e s of the water. This was allowed to stand two days long-er. About two dozen of the animals were used to start a cul-ture. A suspension of 0 . 7 grams of Fleischman's yeast per c c . of water was added to the culture about every third day. The number of animals would r e a c h a peak i n approximately three weeks. Pour such c u l t u r e s were maintained and the s t a r t i n g o f each was staggered so t h a t s u f f i c i e n t numbers of animals were always p r e s e n t . 19. PROCEDURE Be f o r e e x p e r i m e n t a t i o n , the animals were p l a c e d i n a constant-temperature water-bath f o r f o u r t e e n to twenty-four hours. Complete darkness was maintained so t h a t the animals would be dark-adapted. From other e x p e r i m e n t e r * s ' r e s u l t s (Raymont, 1939) i t was c o n s i d e r e d t h a t f o u r t e e n hours was w e l l i n excess o f the time needed f o r d a r k - a d a p t a t i o n . T r a n s -f e r o f the animals to the experimental trough was made w i t h a p i p e t t e i n r e d l i g h t from a General E l e c t r i c NE30 neon glow lamp. An equal number o f animals was p l a c e d i n each compartment o f the experimental trough (see t a b l e s i n Appen-d i x ) . Counts o f t h e i r d i s t r i b u t i o n were made a t time i n t e r -v a l s up to t h i r t y hours a f t e r the experiment was begun. A n i -mals used i n each experiment were d i s c a r d e d on completion o f the t e s t . I n the manner o u t l i n e d , animals were s u b j e c t e d to the f o l l o w i n g c o n d i t i o n s : A. BXPERIMEWTS IN A TEMPERATURE GRADIENT. 1) Does Simocephalus s e r r u l a t u s have a temperature preferendum? ...... i n t r o d u c e animals i n t o a temperature grad-i e n t and note changes i n t h e i r d i s t r i b u t i o n . 2 0 . B. EXPERIMENTS AT A CONSTANT TEMPERATURE (PREFERENDUM) 2) I n a constant temperature would the animals m a i n t a i n random d i s t r i b u t i o n under c o n d i t i o n s i n which no e x t e r n a l s t i m u l u s i s a p p l i e d ? i n t r o d u c e animals i n t o the preferendum tem-p e r a t u r e and note the d i s t r i b u t i o n over a f o l l o w i n g p e r i o d . 3) What i s the response o f the animals t o l i g h t , i f such does e x i s t ? a t a constant temperature (preferendum) sub-j e c t animals to a g r a d i e n t o f l i g h t i n t e n s i t y . 4) What i s the e f f e c t on the animal's response i n a constant temperature o f v a r y i n g r a t e o f r i s e o f l i g h t i n t e n s i t y as a g r a d i e n t ? s u b j e c t animals t o g r a d i e n t s o f v a r i o u s r a t e s o f r i s e o f l i g h t i n t e n s i t y . 5) What i s the e f f e c t on the animal's response i n a constant temperature, o f the a b s o l u t e v a l u e o f l i g h t i n t e n s i t y ? s u b j e c t the animals to l i g h t o f v a r i o u s i n -t e n s i t y l e v e l s i n the preferendum temperature. 6) What i s the e f f e c t on the animal's response a t a constant temperature, o f the d u r a t i o n o f l i g h t . s t i m u l a t i o n ? 21. ..... s u b j e c t the animals to v a r i o u s l e v e l s o f i n t e n s i t y a t the preferendum temperature and note the c h a r a c t e r i s t i c s o f the response. 7) What e f f e c t on the response has p r e a d a p t a t i o n t o l i g h t a t a constant temperature? s u b j e c t animals to l i g h t i n the preferendum temperature a f t e r p r e v i o u s p r e a d a p t a t i o n t o l i g h t o f v a r i o u s i n t e n s i t i e s . 8) What e f f e c t has u l t r a v i o l e t l i g h t on the response at a co n s t a n t temperature? s u b j e c t animals to an i n t e n s i t y g r a d i e n t o f u l t r a v i o l e t l i g h t a t the preferendum temper-a t u r e . 9) What i s the e f f e c t on the response a t a constant temperature o f v a r i a t i o n s i n l i g h t q u a l i t y ? ..... s u b j e c t animals to v a r i a t i o n s i n the q u a l i t y o f the l i g h t source, a t the preferendum temperature. 10) What e f f e c t on the response a t a constant tempera-t u r e has the v a r i a t i o n o f i n t e n s i t y o f the wave-l e n g t h r e g i o n s imposed? s u b j e c t animals to v a r i o u s i n t e n s i t y l e v e l s o f each s p e c t r a l r e g i o n as a g r a d i e n t i n the preferendum temperature. 22. EXPERIMENTS IN A COMBINED LIGHT AND TEMPERATURE GRADIENT. 11) What v a r i a t i o n s i n the response might occur when the animal i s s u b j e c t e d t o g r a d i e n t s o f v a r i o u s wave-length;.regions i n a temperature g r a d i e n t ? ..... s u b j e c t animals t o g r a d i e n t s o f l i g h t q u a l i t y i n a temperature g r a d i e n t . 2 3 . PRELIMINARY EXPERIMENTS  CHARACTERISTICS OF WATER MEDIA To see i f the water used i n the experimental trough had any d e l e t e r i o u s e f f e c t s on t h e ^ n i m a l s ^ t e n animals were put i n 10 c.c.s of water i n th r e e t e s t tubes as f o l l o w s : Tube #1 - F i l t e r e d pond water Tube #2 - C u l t u r e water Tube #3 - Water t h a t had been s t a n d i n g i n the e x p e r i -mental trough f o r twenty-four hours. The tubes were suspended i n one o f the c u l t u r e s t o ensure equal c o n d i t i o n s o f l i g h t and temperature. The curves o f m o r t a l i t y are p l o t t e d i n F i g u r e 14. 30 40 HOURS F i g u r e 14. Comparison o f m o r t a l i t y curves o f animals i n v a r i o u s media. CW -c u l t u r e water. FPW - f i l t e r e d pond water. ETW - water t h a t had been s t a n d i n g i n the experimental trough f o r twenty-four hours. 24. I t i s apparent t h a t no i n c r e a s e i n m o r t a l i t y i s p r e s e n t i n e i t h e r f i l t e r e d pond water or experimental trough water. On the b a s i s o f these r e s u l t s the f i l t e r e d pond water was used i n the experimental trough, and was renewed f o r each experiment. REVERSAL OF PHOTOTACTIC SIGN I t was decided to t e s t f o r r e v e r s a l of the p h o t o t a c t i c s i g n by the w e l l known a c t i o n o f c e r t a i n chemicals on the l i g h t response. The primary response o f Semoceohalus was shown to be p o s i t i v e t o l i g h t and i t was suspected t h a t the a d d i t i o n of chemicals to the water would r e v e r s e the r e -sponse. I f the trough was producing any t o x i c substance t h a t was governing the response, the a d d i t i o n o f such sub-stances would then tend to i n c r e a s e the magnitude o f the l i g h t r e a c t i o n . S o l u t i o n s used were: a) 1 c c . o f 0.5$ S t r y c h n i n e sulphate/100 c c . f i l t e r e d pond water. b) 1.5 c c . 95$ e t h y l a lcohol/200 c c . f i l t e r e d pond water• c) f i l t e r e d pond water w i t h HCl added to g i v e a pH v a l u e o f 3 . 8 . No s i g n i f i c a n t r e v e r s a l i n the response c o u l d be demonstrated. However, the animals f o r m e r l y p o s i t i v e , r e a c t e d almost i n -d i f f e r e n t l y to the i i g h t . 2 5 . Rose (1929) s t a t e s t h a t the a c t i o n o f i n t r o d u c e d chemi-c a l substances may cause other r e a c t i o n s than a r e v e r s a l o f the primary response. He says, c o n c e r n i n g the n a u p l i i o f some s a l t w a t e r p l a n k t o n , " L 1 a d d i t i o n d'une t r a c e d'une sub-stance chimique V l ' e a u ou i l s nagent, peut p r o d u i r e t r o i s e f f e t s d i f f e l r e n t s . . . . l e s animaux deviennent p l u s p o s i t i f s , • , 1 ' i n t e n s i t e du phototropisme n ' e s t pas m o d i f i e e , . , 0 u b i e n e n f i n , l a r i p o s t e phototropique e s t p l u s oujj moins nettement diminuee..•" I t would appear t h a t Slmocephalus r e a c t s i n the second manner, by becoming i n d i f f e r e n t to the l i g h t . I t cannot be s t a t e d whether or not the response I s i n -f l u e n c e d i n any way by the apparatus. The o n l y method on which a c o n c l u s i o n c o u l d be drawn would be t h a t i n which a r e v e r s a l o f the response o c c u r r e d . 26. METHOD FOR TREATMENT OF DATA The r e s u l t s o b t a i n e d i n the s e c t i o n s concerned w i t h the l i g h t r e a c t i o n s at the temperature preferendum, and i n a temperature g r a d i e n t , have been analyzed i n the f o l l o w i n g manner. The h y p o t h e s i s i s f i r s t s e t up t h a t under c o n d i -t i o n s i n which no e x t e r n a l s t i m u l u s i s o p e r a t i n g , animals p l a c e d i n each o f the nine compartments of the e x p e r i m e n t a l trough i n a r a t i o o f 1 : 1 , w i l l m a i n t a i n t h i s "random" d i s -t r i b u t i o n oyer an i n d e f i n i t e p e r i o d o f time. T h e r e f o r e , i f an e x t e r n a l s t i m u l u s i s a p p l i e d t o the sample, the e f f e c t of the s t i m u l u s w i l l m a n i f e s t i t s e l f through a departure from the "random" d i s t r i b u t i o n o f the sample. By t e s t i n g w i t h 1^ the counts o f animals i n each compartment at one time, and the counts i n one compartment at succeeding times, d i f f e r e n c e s i n the random d i s t r i b u t i o n can be shown from the i n i t i a l 1 :1 r a t i o . I n t h i s manner v a r i a t i o n s i n random d i s -t r i b u t i o n can be a t t r i b u t e d e i t h e r to chance v a r i a t i o n or to the o p e r a t i o n o f the e x t e r n a l s t i m u l u s . The degree o f departure from random d i s t r i b u t i o n w i l l then be, i n d i r e c t l y , a measure o f the magnitude o f the animals' response t o the s t i m u l u s . I t then f o l l o w s t h a t the magnitude of the response w i l l a l s o be an i n d i r e c t measure o f the degree o f a c t i v i t y o f the animals i n the magnitude and speed o f the departure from random d i s t r i b u t i o n . The v a l u e s can be d i r e c t l y r e -l a t e d to eachother i n terms o f "X-2, by c a l c u l a t i n g the 27. c o r r e s p o n d i n g c o e f f i c i e n t s o f contingency. These u n i t s can be p l o t t e d to show the pr o g r e s s o f responses and can be i n -t e r p r e t e d as a p r o g r e s s i v e measure o f the animal's a c t i v i t y i n i t s response to the s t i m u l u s . By summing ")L v a l u e s f o r the whole experiment and computing the c o e f f i c i e n t o f con-t i n g e n c y , a measure can be made of t o t a l v a r i a t i o n from r a n -dom d i s t r i b u t i o n . I n experiments i n which, f o r example, the a b s o l u t e i n t e n s i t y i s the v a r i a b l e , t o t a l a c t i v i t y v a l u e s f o r each experiment i n the s e r i e s can be compared. The i n -f l u e n c e o f the f a c t o r i s then shown i n terms o f many counts over a l o n g time p e r i o d . Most o f the da t a upon which the r e s u l t s were based are t a b l e d i n the Appendix. The remain-der i s i n c l u d e d w i t h the Ex p e r i m e n t a l R e s u l t s . The symbols used are ^ i n t e r p r e t e d here. 1) " C h i Square" where S = summation t& s expected frequency a 5 a c t u a l frequency V m " C h i Square" 2) " C o e f f i c i e n t o f Contingency" G W •%* where C s c o e f f i c i e n t o f contingency N - number o f o b s e r v a t i o n s (not number o f c l a s s e s ) 28 The r a t e o f r i s e o f i n t e n s i t y i n the l i g h t g r a d i e n t s has been found i n the f o l l o w i n g manner: where Y = i n t e n s i t y i n compartment n e a r e s t the source. Yo - i n t e n s i t y i n compartment f a r t h e s t from source. n e a base o f Naperiats. l o g a r i t h m s . G n the growth r a t e or r a t e o f r i s e . t m number o f compartments or "time i n t e r v a l s " . 29. EXPERIMENTAL RESULTS  TEMPERATURE PREFERENDUM Experiment 1, F o r t y a d u l t female animals were taken from the c u l t u r e at 17.5°C. and h e l d at 19°C. f o r f o u r t e e n hours. L i g h t i n t e n s i t y , 0.0 f o o t - c a n d l e s . The animals were put i n t o the temperature g r a d i e n t and the d i s t r i b u t i o n determined a f t e r s i x hours. The d a t a are noted i n Ta b l e I I . T a b l e I I . D i s t r i b u t i o n o f animals i n a temperature g r a d i e n t . The tem-p e r a t u r e s g i v e n are those o f the c e n t r e o f each compartment i n the experimental trough. Compartment 1 •. 2 3 4 5 6 7 8 9 Temp. °C. 7.2 9.5 12.2 14 . 7 19.6 23.5 29.0 33.6 33.6 D i s t r i b u t i o n -at Zero Time 5 5 5 5 5 5 5 5 D i s t r i b u t i o n . at S i x Hours 1 4 5 ' 13 10 l 2 The d i s t r i b u t i o n o f the animals i s i l l u s t r a t e d i n F i g u r e 15. The animals i n compartments 1 and 8 have not been i n c l u d e d f o r these reasons: those i n compartment 1 had o b v i o u s l y been so a f f e c t e d by the temperature t h a t they were unable to move out of t h a t r e g i o n . The l o w e r i n g o f the me t a b o l i c r a t e was e v i d e n t i n the slow movements o f the antennae. Consequently, these animals cannot be s a i d to be r e a c t i n g t o the g r a d i e n t i n the same manner as the m a j o r i t y . I t i s t h e r e f o r e f e l t t h a t there I s j u s t i f i c a t i o n f o r e x c l u d i n g them. The animals i n compartment 8 were dead. T h i s p o i n t s to the f a c t t h a t 33.6°C. i s l e t h a l to animals s u b j e c t e d t o the c o n d i t i o n s o f the experiment. I t cannot, however, be c a l l e d the t r u e upper l e t h a l temperature as no estimate o f the r a t e o f a c c l i m a t i o n o f Si,mocephalus to temperature has y e t been c o n s i d e r e d . 12 10 -10 I it ! 8 CMVLRTNE TOTAL i . 10 . 20 30 80 § A4 ! * i X F i g u r e 15. D i s t r i b u t i o n o f animals i n a temper-atu r e g r a d i e n t when p r e v i o u s l y h e l d at 19°C. f o r 14 hours. Animals i n compartments 1 and 8 (Table I I ) have been excluded. The "cumulative t o t -a l " has been p l o t t e d f o r comparison and r e p r e s e n t s the ad d a t i v e t o t a l number o f animals i n p e r c e n t . The preferendum temperature or mean temperature o f ag-g r e g a t i o n has been c a l c u l a t e d f o r the d i s t r i b u t i o n i n a temperature g r a d i e n t . T h i s i s g i v e n i n Tab l e I I I . 31. Table I I I . C a l c u l a t i o n o f the mean temperature of a g g r e g a t i o n or the temperature preferendum from the r e s u l t s o f Experiment 1. Temp.°C.= x No.Animals = f f x 7 .2 — 0 9 . 5 1 95 12 .2 4 4ft e 14.7 5 gtoa.3 19.6 13 61903*0 2 3 . 5 10 55025*0 2 9 . 6 1 Q j M 1 Q 3 3 . 6 — 0 Mean temperature ° C . i s £ £ x = 1 9 # 1 3 o c # The mean temperature o f a g g r e g a t i o n i n a temperature g r a d i e n t or the temperature preferendum, i s found t o be 19.13°C. f o r animals taken from 1 7 . 5 ° C , h e l d at 19°C. f o r 14 hours and counted 6 hours a f t e r b e i n g put i n t o the g r a d i e n t . Experiment 2 . The range o f the temperature g r a d i e n t was decreased to e l i m i n a t e e f f e c t s of temperature extremes observed i n Experiment 1. The decreased temperature range would a l s o demonstrate any v a r i a t i o n i n the r a t e o f response t o g r a d i e n t s teepness . The animals were taken from the c u l t u r e a t 1 7 . 5 ° C , h e l d at 19°C. f o r 14 h o u r s , and then p l a c e d i n the temperature 3 2 . g r a d i e n t ( 15 .0 - 2 3 . 9 ° C ) . The d i s t r i b u t i o n i s i l l u s t r a t e d i n F i g u r e 16. F i g u r e 16. D i s t r i b u t i o n i n a temperature g r a d i e n t o f animals p r e v i o u s l y h e l d a t 19°C. f o r 14 hours (See F i g u r e 1 5 ) . That the steepness o f the temperature g r a d i e n t has an e f f e c t on the response o f the animals can be seen by com-p a r i n g the d i s t r i b u t i o n curves i n Experiments 1 and 2 . Where the steepness o f the g r a d i e n t i s l e s s , the tendency t o move i n t o a preferendum temperature decreases. I t i s suggested t h a t the s t i m u l u s promoting the r e a c t i o n to tem-pe r a t u r e changes v a r i e s i n i n t e n s i t y w i t h the r a t e o f change of temperature to which the animal i s s u b j e c t e d . RANDOM DISTRIBUTION Experiment 3 . B e f o r e proceeding w i t h the s t u d i e s o f the response t o l i g h t a t the preferendum temperature a 33. second t e s t was made to see i f the apparatus had any e f f e c t on the d i s t r i b u t i o n of the animals. I f a constant number of animals were introduced into each compartment, with no external stimulus operating, the animals should maintain "random d i s t r i b u t i o n " . Variations from the i n i t i a l 1:1 r a t i o of d i s t r i b u t i o n could be tested to see whether or not they occurred by chance alone. Twenty-seven adult females were taken from the culture at 17 .5°C and held at 19°C. for 18 hours. (Light i n t e n s i t y , 0.0 foot-candles) The animals were put i n the experimental trough and remained i n darkness for the duration of the ex-periment. The r e s u l t s are given i n Table IV (Appendix), The regression c o e f f i c i e n t has been calculated f o r the d i s t r i b u t i o n of the animals. From the value given i n Table V i t i s evident that the d i s t r i b u t i o n i s not dependent on any factor inherent i n the apparatus. Table V. Cal c u l a t i o n of the regression of the number of animals i n each compartment on compartments. SX = 4-5 Compartment No.Animals X Y 1 l.b 2 2.0 4.0 4 1.5 5 1,5 6 2.6 7 2.1 8 4.6" 4.1 - 45 24.6 = 5 2.7 • 5 ^ = 5 X Y - ( S M ( S Y ) / M = - 0 3 O O O S " The regression l i n e i s found by substituting values i n the equation: y - G + b ( - x - ^ ) 34. The regression line has been plotted i n Figure 17 to show the relationship existing between the compartments and the number of animals i n each compartment. It i s seen to be very close to random distribution. 3 * CO/IPWTMEtlT Figure 17. Graph of the regression of the number of animals i n each compart-ment or compartments. GRADIENTS OF LIGHT INTENSITY The responses to light were studied at the preferendum temperature. Animals were subjected to gradients of light at different intensities and various rates of r i s e . The results are tabulated in Experiments 4 to 12 (Tables V I I I tp XVI, Appendix). 3 5 . The d e t a i l s o f Experiments 4 to 12 are l i s t e d i n T a b l e V I . I n a l l cases the animals were h e l d , p r e v i o u s to use, a t 19°C. i n t o t a l darkness. T a b l e V I . D e t a i l s o f procedure f o r Experiments 4 to 12. Experiment No. No. o f Animals Time h e l d at 19°C.(Hrs.) I n t e n s i t y L i m i t s o f the L i g h t G r a d i e n t Used (Fo o t - c a n d l e s ) 4 27 14 0.025 - 0.122 5 27 19 0.010 - 1.54 6 27 19 0.007 - 7 .2 7 27 15 0.222 - 1.32 8 27 15 0.006 - 0.500 9 27 15 1.1 - 3 6 . 0 10 27 14 . 5 1.1 - 4 8 . 6 11 27 14 1.8 - 4 7 . 7 12 27 18 9 . 0 - 6 0 . 1 The c h a r a c t e r i s t i c s o f the responses i n Experiments 4 t o 12 are l i s t e d i n Ta b l e V I I . T a b l e V I I . C h a r a c t e r i s t i c s o f the response to 36. the c o n d i t i o n s imposed by the l i g h t - g r a d i e n t s i n Experiments 4 to 12.  E x p e r i -ment No. Rate o f R i s e o f I n t e n s i t y 4 I n t e n s i t y i n Comp't'mt (Foot-c a n d l e s ) »C"Value f o r Time Count a t 6 hours Time (Hrs) to Peak o f Response "C" Value of peak Response 4 .16 .122 .387 4 .548 5 .56 1.54 .797 3 .787 6 .77 7.2 .759 2 i .775 7 .66 1.32 .510 14 .843 8 .49 .500 .766 1* .812 9 .39 36.0 .791 .883 10 .42 48.6 .570 ^ .608 11 .36 47.7 .566 3 .735 12 .21 60.1 .560 3 .693 A Loge i n t e n s i t y r i s e Loge compartments A. Stimulus I n t e n s i t y , and Magnitude o f Response. As the f i n a l i n t e n s i t y , or the i n t e n s i t y at the end o f the g r a d i e n t c l o s e s t to the source i s i n c r e a s e d , the magni-tude o f the response f i r s t r i s e s s h a r p l y and then d e c r e a s e s . The animals have an a b s o l u t e optimum l i g h t i n t e n s i t y f o r a c t i v i t y a t approximately 5 f o o t - c a n d l e s . T h i s i s i l l u s -t r a t e d i n terms o f : the number o f animals b e i n g " a t t r a c t e d " t o the f i n a l i n t e n s i t y compartment ( F i g u r e 18), t o t a l a c t i v -i t y ( F i g u r e 19), or the v a l u e o f C f o r the d i s t r i b u t i o n a t 6 hours ( F i g u r e 20). The composition o f the l i g h t v a r i e d , however, the lamps o f h i g h e r wattage producing more b l u e l i g h t than those o f lower wattage. T h i s f a c t o r w i l l be 37 . d i s c u s s e d l a t e r . I n cases where the lamp was moved, not s u b s t i t u t e d by another, t o g i v e h i g h e r or lower i n t e n s i t i e s , the r e s u l t i n g d i s t r i b u t i o n s t i l l f o l l o w s the g e n e r a l t r e n d . The author then f e e l s j u s t i f i e d i n s t a t i n g t h a t there i s a true optimum l i g h t i n t e n s i t y f o r the animals. 2 0 10 ZO 30 40 50 60 INTENSITY IN COnPARTMEHT N£fltf£Sr $ o y « C € (FOQT-CaNOLCS) F i g u r e 18. R e l a t i o n s h i p between i n t e n s i t y o f s t i m u l a t i o n and the number of animals a r r i v i n g a t the compartment n e a r e s t the l i g h t . 3 8 . 10 20 30 40 50 (aO INTENSITY IN COMPARTMENT NC/VieST SOl/tCB Figure 19 . Relationship between i n t e n s i t y of stimulation by l i g h t i n terms of the response as the f i n a l t o t a l value of C f o r each ex-periment. •too / m J ~ _ o r O L _ i —1 1 1 1 10 20 30 <W) 50 IHTEHSITy Hi CQMPAHTMCNT fiEtyi£ST SOUHCE (fOOT-CH.SOLES) Figure 20. Relationship between i n t e n s i t y of stimulation and the response i n terms of the value of C f o r the d i s t r i b u t i o n at 6 hours. The relationship between i n t e n s i t y and the magnitude the response i s also shown by the value of C at the time 3 9 . o f the peak o f the response ( F i g u r e 21). MM) r a - L u id 20 30 40 50 60 iNTtNSrry in corrPAHTMenr nenaesr SOURCE ^ (POOT-CaHOLCS) F i g u r e 21. R e l a t i o n s h i p between i n t e n s i t y and the v a l u e o f C a t the time o f the peak o f the response. B. Stimulus I n t e n s i t y and Rate o f Response. F o r the purpose o f comparing the i n t e n s i t y l e v e l and the speed w i t h which the f i n a l d i s t r i b u t i o n i s assumed, the time a t which the peak i n the movement toward the l i g h t o c c u r r e d i s c o n s i d e r e d . The r e s u l t s show no c o r r e l a t i o n between the i n t e n s i t y l e v e l and the r a t e o f the response. No s i g n i f i c a n c e i s att a c h e d to t h i s statement. I t i s con-s i d e r e d t h a t the data are not adequate to a s s e r t whether there i s any a s s o c i a t i o n . C. Rate o f R i s e o f I n t e n s i t y and the Magnitude o f the Response. The r e l a t i o n s h i p between the r a t e o f r i s e o f i n t e n s i t y i n the g r a d i e n t and the magnitude of the response i s 4 0 , i l l u s t r a t e d i n F i g u r e 22. The degree o f mass movement toward the l i g h t i n c r e a s e s as the i n t e n s i t y i n c r e a s e s and l e v e l s o f f at a maximum v a l u e . T h e r e f o r e , the animal must be s t i m u l a t e d to move to h i g h e r l i g h t i n t e n s i t i e s through "comparison" o f i n t e n s i t y l e v e l s as i t moves about i n the trough. RFTTE OF RISE. OF INTEHSIT* F i g u r e 22. R e l a t i o n s h i p between the r a t e o f r i s e o f i n t e n s i t y i n the g r a d i e n t and the magnitude; o f the response i n terms o f C a t 6 hours. A l s o i l l u s t r a t e d i s the time taken f o r the response t o r e a c h a peak i n the movement toward the l i g h t . I t appears from a comparison o f the d a t a i n the l a s t two s e c t i o n s t h a t the response to a g r a d i e n t o f l i g h t 41. i n t e n s i t y depends on the r a t e a t which the l i g h t i n t e n s i t y changes w i t h i n a g r a d i e n t , and not on the i n t e n s i t y l e v e l . D. Rate o f R i s e o f I n t e n s i t y and the Rate o f the Response. The r a t e o f r i s e o f l i g h t i n t e n s i t y i n a g r a d i e n t i s i n v e r s e l y c o r r e l a t e d w i t h the time f o r the maximum v a l u e o f a c t i v i t y to occur. ( F i g u r e 22) As the r a t e o f r i s e i n c r e a s -es, the time f o r the g r e a t e s t v a l u e o f the response t o occur p r o g r e s s i v e l y d ecreases. E. I n t e n s i t y and D u r a t i o n o f Response. When animals are su b j e c t e d t o l i g h t s t i m u l i o f i n c r e a s -i n g i n t e n s i t y , the response i s lo n g e r i n d u r a t i o n a't lower i n t e n s i t i e s . The animals tend to r e d i s t r i b u t e themselves toward the r e g a i n i n g o f random d i s t r i b u t i o n a f t e r the peak o f the p h o t o t a c t i c response,has been reached. T h i s occurs more q u i c k l y a t h i g h e r l i g h t i n t e n s i t i e s . The r e s u l t s suggest t h a t the r a t e o f a d a p t a t i o n to l i g h t i n t e n s i t y i s d i r e c t l y r e l a t e d to the i n t e n s i t y o f the source o f s t i m u l a t i o n (see F i g u r e 23). 42 10 15 20 DUH8TI0N OF STIMULATION (HG&.) F i g u r e 2 3 . R e l a t i o n s h i p between the d u r a t i o n o f response and the i n t e n s i t y o f the source o f l i g h t a c t i n g as the s t i m u l u s . PREADAPTATION The response to l i g h t o f dark-adapted animals has been c o n s i d e r e d i n the p r e v i o u s s e c t i o n s . The r e a c t i o n to l i g h t i s now demonstrated f o r animals h e l d under co n s t a n t i l l u m -i n a t i o n b e f o r e e x p e r i m e n t a t i o n . T h i s source o f i l l u m i n a t i o n , or p r e a d a p t a t i o n s t i m u l u s was v a r i e d i n i n t e n s i t y i n E x p e r i -ments 13 and 14. The r e a c t i o n s o f the animals to the i n -t e n s i t y l e v e l o f p r e a d a p t a t i o n s t i m u l u s were then e v a l u a t e d 43. by comparison o f t h e i r response t o those of dark-adapted animals. The degree o f a c t i v i t y demonstrated under c o n d i t i o n s i n which no e x t e r n a l s t i m u l u s i s o p e r a t i n g has been found i n Experiment 3. T h i s v a l u e i s shown i n F i g u r e 24. The magni-tude o f the response to the l i g h t source i n a c o n s t a n t I n -t e n s i t y g r a d i e n t , when the animals are s u b j e c t e d t o v a r i a -t i o n s i n the p r e a d a p t i n g s t i m u l u s , i s shown i n F i g u r e 24, The response i s shown to be d i r e c t l y r e l a t e d to the i n t e n s i t y o f the p r e a d a p t i n g source. I t i s to be remembered t h a t the experiment demonstrates o n l y one s p e c i a l case i n which the animals were h e l d at 20°C. b e f o r e and throughout the e x p e r i -ment. I f the temperature were to be v a r i e d , the h e i g h t o f  the graph from the b a s e l i n e would v a r y , being h i g h e r as the temperature i n c r e a s e d and lower as the temperature decreased. These v a r i a t i o n s would then be measures o f the a c t i v i t y f o r the response a t v a r i o u s l e v e l s of the metabolic r a t e . Changes i n the slope o f the l i n e would then suggest d i f f e r -e n t i a l r a t e s o f a c t i v i t y i n c r e a s e to the p r e a d a p t i n g s t i m u l u s f o r d i f f e r e n t m e t abolic r a t e s . The d a t a f o r Experiments 13 and 14 are found i n T a b l e s XVII and XVIII (Appendix). 44. 10 .75 i V - 5 0 •25 Q 2 4 * 8 >o \i w STIMULUS (P0QT - CAHOLfS) F i g u r e 24. R e l a t i o n s h i p between the degree o f a c t i v i t y o f the response i n terms o f C w i t h v a r i a t i o n s i n the i n t e n -s i t y o f the p r e a d a p t a t i o n s t i m u l u s . ULTRA-VIOLET LIGHT The u l t r a - v i o l e t lamp was s e t up a t one end o f the ex-pe r i m e n t a l trough so t h a t a g r a d i e n t o f i n t e n s i t y was p r o -duced from one end o f the troug h t o the o t h e r . The r e s u l t s o f the experiment are g i v e n i n T a b l e XIX, Experiment 15 (Appendix). The nature and prog r e s s o f the response are i l l u s t r a t e d i n F i g u r e 25. 45. HOURS * ' * H \ \ % \ I |fe "I < 1 — — i r r 1 i r J 1 1 L i » ' F i g u r e 25. Nature and progress o f the response to u l t r a - v i o l e t l i g h t i n terms o f C. There i s a r e v e r s a l i n the p h o t i c r e a c t i o n . The a n i -mals move away from the source whereas the response to v i s -i b l e l i g h t was found to be p o s i t i v e , the animals moving toward the source. WAVE LENGTH OF VISIBLE LIGHT Lamps were arranged over f i l t e r s , s et on top o f the o p a l g l a s s , so t h a t each compartment was s u b j e c t e d to the 46. same i n t e n s i t y of i l l u m i n a t i o n . The f i l t e r s were arranged i n a graded s e r i e s , p r o g r e s s i v e l y removing more o f the s h o r t -er wave-lengths u n t i l o n l y i n f r a - r e d l i g h t was t r a n s m i t t e d i n the l a s t compartment. The data are presented f o r three t e s t s made under these c o n d i t i o n s a t 2.7, 5.4 and 18.0 f c . ( T a b l e s XX, XXI, XXII, Appendix^ experiments 16 to 18 r e s p e c t -i v e l y ) . The d i s t r i b u t i o n o f the animals i s i l l u s t r a t e d In F i g u r e 26. F i g u r e 26. D i s t r i b u t i o n o f animals at equal i n t e n s i t i e s (2.7, 5.4 and 18.0 f c . ) i n a s e r i e s of graded wave-lengths o f v i s i b l e l i g h t . The animals aggregated i n the r e g i o n i n which the blue end o f the spectrum was t r a n s m i t t e d . The peak o f the d i s t r i b u t i o n o c c u r r e d under the o p a l g l a s s w i t h no f i l t e r . The l i g h t r e a c h i n g the animals i n t h a t compartment would ex-tend i n wave l e n g t h from the approximate l i m i t s o f 34-00 A* i n t o the i n f r a - r e d r e g i o n . The animals t h e r e f o r e show the g r e a t e s t p h o t o t a c t i c response to l i g h t i n the blue end o f the spectrum. SPECTRAL REGIONS OF GRADED INTENSITY The s e r i e s o f graded f i l t e r s was used to set up l i g h t g r a d i e n t s o f equal i n t e n s i t y and r a t e o f r i s e so t h a t the o n l y v a r i a b l e would be wave l e n g t h . The r e s u l t s o f these experiments are t a b u l a t e d i n T a b l e s XXIII to XXVIII, E x p e r i -ments 19 to 24 r e s p e c t i v e l y (Appendix). The c h a r a c t e r i s t i c s o f the l i g h t response are i l l u s t r a t e d i n F i g u r e s 27 and 28. F i g u r e 27 i l l u s t r a t e s the s p e c t r a l s e n s i t i v i t y of the a n i -mals. The s e n s i t i v i t y to l i g h t r i s e s from zero a t 6400 X, reaches a peak i n the r e g i o n o f 4000 % and d e c l i n e s towards the u l t r a v i o l e t . The approximate Wave l e n g t h r e g i o n a t which the r e v e r s a l o f p h o t o t a c t i c response occurs i s i l l u s -t r a t e d and would be a t approximately 3000 - 3500 A*. How much the animals would be a f f e c t e d by these s h o r t e r wave le n g t h s i s worthy of c o n s i d e r a t i o n . The e x t i n c t i o n c o e f f i c -i e n t s f o r waverlengths from 3030 to 6120 % are i l l u s t r a t e d f o r comparison. The amounts o f l i g h t t r a n s m i t t e d i n the s h o r t blue and l o n g u l t r a - v i o l e t r e g i o n s i n the n a t u r a l h a b i t a t would be much s m a l l e r than t h a t t r a n s m i t t e d i n the long e r v i s i b l e wave l e n g t h s from 4000 to 6000 ft. spEcrafiL set/sirivtry X 1 - 2o 4 0 E * r O feo * 3ooo 4000 5ooo feooo ! TX*NSf1/SS/QH LIMITS OP FILTERS, AM<i STXOMS F i g u r e 27. S p e c t r a l s e n s i t i v i t y curve i n terms o f the a c t i v i t y v a l u e o f the response. 49. NUM6ER REFERS TO FILTER USED HOURS i : F i g u r e 28. P r o g r e s s o f the response t o l i g h t i n g r a d i e n t s o f equal r a t e o f r i s e and i n t e n s i t y , where the wave l e n g t h s t r a n s -m i t t e d are p r o g r e s s i v e l y omitted from the b l u e end o f the spectrum t o the r e d . An i n t e r e s t i n g f e a t u r e i l l u s t r a t e d i n F i g u r e 28 i s the decrease o f the response to t o t a l i l l u m i n a t i o n below t h a t f o r the l i g h t t r a n s m i t t e d by the f i l t e r e x c l u d i n g wave l e n g t h s below.3900 A*. T h i s would s u b s t a n t i a t e p r e v i o u s d a t a i n which the peak o f the l i g h t response occurs at approximately 4000 A*. The response to the r e d end o f the spectrum not o n l y decreases i n magnitude but a l s o tends t o be e r r a t i c . I t i s p o s s i b l e 5 0 . t h a t animals adapt to the longer wave l e n g t h s more q u i c k l y , or t h a t the stimulus i s l e s s i n t e n s e i n promoting the r e -sponse. An animal adapted to the l i g h t might then be s t i m -u l a t e d by i t a g a i n through the g e n e r a l movements o f the a n i -mal i n the g r a d i e n t o f i n t e n s i t y . COMBINED LIGHT AND TEMPERATURE GRADIENTS WITH WAVE LENGTH  VARIATIONS. Simocephalus has been shown to be p o s i t i v e l y p h o t o t a c -t i c t o v i s i b l e l i g h t above the r e g i o n commencing at 4000 A*. T h i s response decreases toward the r e d end o f the spectrum. Responses i n a temperature g r a d i e n t have been shown to p r o -duce a c o n c e n t r a t i o n p o i n t i n a temperature g r a d i e n t o f ap-p r o x i m a t e l y 20°C. f o r animals p r e v i o u s l y h e l d at 19°C. I n the f o l l o w i n g s e c t i o n these two f a c t o r s have been opposed i n a manner so as to antagonize the responses to l i g h t and i n -c r e a s e s i n temperature. The d i r e c t i n g i l l u m i n a t i o n was l o -cated a t the h i g h temperature end o f the g r a d i e n t . The f i r s t t e s t determined the d i s t r i b u t i o n i n the temperature grad-i e n t w i t h no l i g h t s t i m u l u s o p e r a t i n g (see F i g u r e 29). I n t h i s case i t i s seen t h a t the 5 0 p e r c e n t l i n e i s c r o s s e d by the graph o f a d d i t i v e percentage o f the t o t a l number o f a n i -mals, a t 20°C. The s t r a i g h t l i n e r u n n ing to d i a g o n a l c o r n e r s r e p r e s e n t s the d i s t r i b u t i o n expected i f no response to tem-p e r a t u r e d i f f e r e n c e s o c c u r r e d . The lower p a r t o f the graph of a c t u a l d i s t r i b u t i o n s i g n i f i e s a movement away from the 51. temperatures i n t h a t r e g i o n . The upper p a r t o f the l i n e , however, s i g n i f i e s aumovement i n t o the temperature r e g i o n a-bove t h a t which would be expected i f temperature were not a c t i n g as a d i r e c t i n g i n f l u e n c e . I n t h i s l a t t e r r e s p e c t , i t has been e s t a b l i s h e d t h a t c o l d - b l o o d e d animals moving i n t o a r e g i o n o f c o l d e r temperature, a d j u s t p h y s i o l o g i c a l l y t o the d i f f e r e n c e by a decrease i n m e t a b o l i c r a t e . I n such a c o n d i t i o n , a c t i v i t y would decrease and t h e r e would develop an a g g r e g a t i o n i n t h i s colder.temperature r e g i o n which, by v i r t u e of the method at which the a g g r e g a t i o n o c c u r s , would d i f f e r from the temperature preferendum. I t i s suggested t h a t i n a r r i v i n g at the temperature preferendum, ah a l t e r n a t e procedure would be r e s p o n s i b l e . I t would be brought about through c e s s a t i o n of a c t i v i t y by a r r i v a l i n a temperature to which the animal-has been p r e v i o u s l y s u b j e c t e d . T h i s temperature would produce the l e a s t s t i m u l a t i o n a r i s i n g through d i f f e r e n c e s i n the temperature exposed to a t the moment and those d i f f e r e n t temperatures e x i s t i n g around i t . To i n t r o d u c e the second s t i m u l u s then imposes a prob-lem: w i l l the animals o r i e n t to one f a c t o r , the o t h e r f a c -t o r , both, or a compromise o f both? When the animals are su b j e c t e d t o a g r a d i e n t o f l i g h t i n t e n s i t y i n a temperature g r a d i e n t there i s a d i f f e r e n c e i n the d i s t r i b u t i o n a t t a i n e d from those f o r each f a c t o r o p e r a t i n g s e p a r a t e l y (see F i g u r e 29). From the graphs o f d i s t r i b u t i o n under the v a r i o u s g r a d i e n t s of q u a l i t y at e q u a l i n t e n s i t i e s the f o l l o w i n g 52. changes are noted from the c o n d i t i o n i n which l i g h t was ab-sent. The g r e a t e r the i n c l u d e d p o r t i o n o f the spectrum, o r the w h i t e r the l i g h t i s , the g r e a t e r i s the a t t r a c t i o n i n t o the warm end which was p r e v i o u s l y avoided. The p o i n t a t which the graph c r o s s e s the 50 p e r c e n t l i n e o f d i s t r i b u t i o n i s then moved toward the warm end to the l e f t o f 20°C. How-ever, i f the temperature was con s t a n t a t , say 2 0 ° C , the a n i -mals would migrate t o the end o f the trough n e a r e s t the l i g h t (compare w i t h Experiment 5, T a b l e IX, Appendix). The con-c l u s i o n i s then reached t h a t the two f a c t o r s produce a com-promise response. In such a procedure as t h i s , the s h i f t ' t o w a r d the l i g h t c o u l d a l s o be produced by i n c r e a s e s i n l i g h t i n t e n s i t y . Such an i n c r e a s e would r e s u l t i n a curve o f maximum response. The area i n c l u d e d w i t h i n t h i s curve and the curve o f d i s t r i b u t i o n i n darkness would then be a measure o f a c t i v i t y p o s s i b l e under the c o n d i t i o n s o f temperature e s t a b l i s h e d by the experiment. F i g u r e 30 i l l u s t r a t e s the d i f f e r e n c e s i n a c t i v i t y v a l u e s under c o n d i t i o n s o f v a r i a b l e l i g h t q u a l i t y i n a form l i m i t e d to the present d a t a . By c o n s u l t i n g T a b l e s XXIX to XXXII, Experiments 25 t o 28 r e s p e c t i v e l y (Appendix), i t i s seen t h a t the p a r t o f the gr a d i e n t d i s c u s s e d above I s l i m i t e d to the compartments o f temperatures 30.0°C. to 16.1°C. The i n c l u s i o n o f the a n i -mals i n compartments o u t s i d e o f t h i s range would, i t i s f e l t , u n n e c e s s a r i l y weight the r e s u l t s and obscure the f a c t s a t hand. 53. Above 30°C. v e r y l i t t l e change i n d i s t r i b u t i o n i s shown to occur, (one exception). The animals i n t r o d u c e d i n t o these compartments were not, i t i s surmised, able t o move out o f those r e g i o n s b e f o r e death ensued. Brown (1929) has de-s c r i b e d r e l a t i v e l e t h a l temperatures f o r a number o f C l a d -oceran s p e c i e s by immersing the animals i n water heated t o d e s i r e d temperatures and t a k i n g the temperature a t which the animal d i e d a f t e r one minute exposure as the " r e l a t i v e " l e t h a l temperature. He p o i n t s out t h a t t h i s i s not a t r u e a b s o l u t e v a l u e . For £ . e x p i n o s i s and v e t u l u s the r e l a t -i v e l e t h a l temperatures were 43°C. That the l e t h a l tempera-t u r e o f £ . s e r r u l a t u s under the p r e s e n t c u l t u r e c o n d i t i o n s i s lower than t h i s , i s c e r t a i n ^ a s 100 percent o f those a n i -mals a t 35.8°C. d i e d w i t h i n one h a l f hour. The d i f f e r e n c e s as shown i l l u s t r a t e the n e c e s s i t y o f d e f i n i n g standard t e c h -n i q u e s . I t must be a s s e r t e d here t h a t no t r u e l e t h a l tem-p e r a t u r e v a l u e s can be d e s c r i b e d without knowledge o f the p r e v i o u s thermal h i s t o r y . F r y (1947)A B r e t t (1946.., .1944) have used a system o f a r r i v i n g a t these v a l u e s i n which the time f a c t o r and the p r e v i o u s thermal h i s t o r y are c o n s i d e r e d . The temperature a t which 50 percent o f the animals d i e a f t e r 12 hours when p r e v i o u s l y a c c l i m a t e d to a s p e c i f i c tempera-t u r e i s regarded as the a b s o l u t e l e t h a l temperature. Very l i t t l e movement i n t o these r e g i o n s o c c u r r e d and such as d i d occur c o u l d f a l l w e l l w i t h i n the r e a l m o f change movements. Below 16.1°C, the animals appear to become trapped by the 54. l o w e r i n g o f the metabolic r a t e and consequent decrease i n a c t i v i t y . Brown (1929) s u b j e c t e d v a r i o u s s p e c i e s of C l a d o c e r a to temperatures near 0°C. and found t h a t responses f e l l i n t o two groups. I n one group, c e r t a i n s p e c i e s became immediately i n a c t i v e w h ile i n the other group, which i n c l u d e d S. s e r r u l -a t u s , animals remain a c t i v e i n d e f i n i t e l y . I n the present case a c t i v i t y was v i s i b l y slowed, the antenna movements b e i n g much reduced i n frequency. The animals below and above ap-pro x i m a t e l y l6.1°C. then comprise two d i s t i n c t p o p u l a t i o n s ( w i t h o v e r l a p p i n g around 1 6 . 1°C). T h e i r response t o l i g h t as a stimulus w i l l proceed a t two d i f f e r e n t r a t e s . The two groups cannot be t r e a t e d as one f o r t h i s reason. Another c o n s i d e r a t i o n t o d i s c u s s concerning p o s s i b l e changes i n the primary p h o t o t r o p i c response i s t h a t p o s i t i v e p h o t o t r o p i c animals moving i n t o warmer temperatures show a r e v e r s a l i n primary s i g n ( C l a r k e , 1932)'. Such animals when moving i n t o c o l d e r temperatures have been shown to have an enhanced primary s i g n . I n the present case t h i s would r e s u l t i n a l e s s e n i n g o f the l i g h t r e a c t i o n as an animal migrated t o warmer water and a s t r e n g t h e n i n g o f the r e a c t i o n w i t h m i g r a t i o n t o c o l d e r water. The former p o s s i b i l i t y i s agreeable. The l a t t e r i s p o s s i b l e i f such a change i n response might be expected to o f f s e t t o some extent the " t r a p p i n g " e f f e c t o f the c o l d water below 16.1°C. In T a b l e s XXIX t o XXXII (Appendix), there i s a decrease i n numbers trapped i n the c o l d e r end when l i g h t 5 5 . i s o p e r a t i n g . T h i s may be, however, due to the f a c t t h a t l i g h t as a d i r e c t i v e f a c t o r was not o p e r a t i n g i n the f i r s t t e s t (Table XXIX), hence no f a c t o r other than temperature would be i n f l u e n c i n g the animals i n t h e i r movements. In t h i s r e s p e c t the f o l l o w i n g theory i s presented. The degree of a c t i v i t y at a constant temperature o f 20°C. f o r a g r a d i e n t o f i n t e n s i t y such as t h a t i n Experiment 5 (Table IX, Appen-di x ) ^ i s . 7 8 . The degree of a c t i v i t y i n a temperature grad-i e n t i n darkness as t h a t i n Experiment 2 5 (Table XXIX, Appen-dix)} i s . 6 . I f c o n d i t i o n s producing these measures o f a c t i v -i t y , c o n s i d e r e d as " f o r c e s producing a response", (they are measures o f magnitude) are set up so as t o be opposing, would the r e s u l t i n g response be t h a t o f t h e i r d i f f e r e n c e ? I f such were the case, then no changes i n the primary l i g h t response need be c o n s i d e r e d f o r animals moving through a range i n temperatures. I t would then become a f u n c t i o n o f two opposing f o r c e s . Such an i d e a i s expressed g r a p h i c a l l y below. F 2 " F l Z . 1 7 8 ? i - Experiment 2 5 F2 - Experiment• 5 . 7 8 " The excess o f F 2 w i l l then decrease F^ by ( F 2 - F.^) to give .42, To t e s t t h i s r e s u l t a comparison i s made of the v a l u e o f a c t i v i t y o c c u r r i n g i n a case i n which the f a c t o r s here c o n s i d e r e d s i n g l y would be combined. The a c t i v i t y v a l u e o f F l -. 6 F 2 z 5 6 . such a case I s taken from T a b l e XXX (Appendix), which answers the necessary c o n d i t i o n s , the v a l u e being .46, f a i r l y c l o s e to .42. Thus j&Fjfc - ( F 2 - Fj) = R where F 2 = g r e a t e r a c t i v i t y v a l u e o f Force A ( l i g h t ) F^ s l e s s e r a c t i v i t y v a l u e o f Force B (Temperature) R 3 r e s u l t i n g combined response i n terms o f a c t i v i t y . C l a r k e ( 1 9 3 0 ) has shown f o r Daphnia t h a t primary s i g n s do change w i t h temperature changes. The p r e c e d i n g argument may be a s p e c i a l case but i s f e l t worthy o f c o n s i d e r a t i o n . There i s a major d i f f e r e n c e i n the apparatus o f C l a r k e ' s work-to be c o n s i d e r e d . I n h i s experiments l i g h t d i r e c t i o n was a c t i n g as a d i r e c t i n g f a c t o r w h ile here l i g h t i s o p e r a t -i n g i n a n o n - d i r e c t i o n a l g r a d i e n t . Figure 29. Illustration of distribution i n a tem-perature gradient where the light grad-ient imposed simultaneously, varies i n composition. •7S CONTROL IN DMKHCSS •50 o ° t 1 •1$ ' • 3ooo 4000 500O fcooo TRftHSMlSStOH LIMITS Or fiLTKRS, RN4STR0MS Figure 3 0 . Illustration of the differences in activity i n a temperature gradient where the light.-gradient imposed simultaneously/varies in composition. 58. DISCUSSION TEMPERATURE PREFERENDUM Simocej^hains. has been shown to aggregate i n a zone o f temperature w i t h i n a l a r g e r temperature range . T h i s " t e m -p e r a t u r e preferendum" or "preferendum" has a mean v a l u e o f 19.13 ° C when the animals p r e v i o u s l y are h e l d a t 19°C. It i s i n t e r e s t i n g to note t h a t the temperature preferendum i s o f a h i g h e r order than the temperatures t o which Simocephalus would u s u a l l y be sub jec ted i n the normal environment . The temperature preferendum cannot , t h e r e f o r e , be des ignated as a temperature o f h a b i t a t p r e f e r e n c e . Doudorof f (1938) , working w i t h G i r e l l a n i g r i c a n s (Ayres) found t h a t when these f i s h were • c o n d i t i o n e d ' to 10°C. they would always move i n t o a h i g h e r temperature t h a n 10°C. i n a temperature g r a d i e n t . He concludes t h a t " . . . s e l e c t i o n i n a g r a d i e n t i s not a r e l i a b l e i n d e x or measure o f a c c l i m a t i z a t i o n " , f o r , i f the animals remain exposed to the " temperature preferendum" i n a g r a d i e n t , they w i l l e v e n t u a l l y become a c c l i m a t i z e d to i t and w i l l move to s t i l l h igher temperatures than the f i r s t temperature preferendum. That the temperature preferendum does bear a d i s t i n c t r e l a t i o n s h i p to the thermal h i s t o r y o f the an imal i s i l l u s t r a t e d by F r y (194-7); the temperature p r e -ferendum f o r Carassius auratus r i s e s as the a c c l i m a t i o n tem-p e r a t u r e i n c r e a s e s . The preferendum u l t i m a t e l y l e v e l s o f f a t the " f i n a l preferendum" at which no f u r t h e r i n c r e a s e i n 59. the p r e f e r r e d temperature w i l l occur w i t h f u r t h e r r i s e s i n a c c l i m a t i o n temperature. A t t h i s " f i n a l preferendum" the p r e f e r r e d temperature i s equal t o the a c c l i m a t i o n tempera-t u r e . The s i g n i f i c a n c e o f the temperature preferendum has not y e t been e s t a b l i s h e d . F r y (1947)» summing up the l i t e r -a ture i n t h i s r e s p e c t , p o i n t s out t h a t the temperature p r e -ferendum shows a p o s s i b l e r e l a t i o n to optima f o r a c t i v i t y . When Car as sins auratus i s t h e r m a l l y adapted to temperatures at which the c r u i s i n g speeds are measured, a r e l a t i o n i s seen to e x i s t between t h i s speed and the r e g i o n o f the f i n a l preferendum. The c o r r e l a t i o n does not e x i s t f o r f i s h not p r e v i o u s l y adapted to the temperatures a t which the c r u i s i n g speeds were measured. F r y suggests t h a t t h i s l a c k o f c o r -respondence i s of v a l u e to the g o l d f i s h by government o f the response t o a temperature g r a d i e n t i n b r i n g i n g the f i s h i n t o a p o t e n t i a l zone o f optimum a c t i v i t y when i t has become ac c l i m a t e d t o t h a t zone. I n the present study i t was not proposed to develop the r e l a t i o n s h i p s e x i s t i n g between the temperature preferendum at v a r i o u s l e v e l s of a c c l i m a t i o n and succeeding f a c t o r s . I t was however, d e s i r e d t o have a standard r e p r o d u c i b l e temper-ature c o n d i t i o n o f known q u a l i f i c a t i o n s upon which f u r t h e r s t u d i e s of the d e s i r e d nature c o u l d be based. 60. RESPONSE TO GRADIENTS OF LIGHT INTENSITY Gradients of light intensity have been used to test the responses of Simocephalus to lig h t . Such characteristics of the stimulus as intensity, rate of rise of intensity In a gradient, and the duration of stimulation, have been con-sidered. The primary phototactic response has been found to be positive for Simocephalus serrulatus at 20°C. The use of gradients of temperature and light intensity, as employed i n the present study, must be viewed with dis-cretion when interpreting responses to natural conditions. It i s probably very seldom that such steep gradients of the factors considered would be found to occur naturally. S t i l l , in order to understand how each environmental factor affects distribution under normal conditions, some means of separat-ing each factor for individual study must be developed. Only by the interpretation of data gained from standard pro-cedures can various phenomena be correctly evaluated. The setting up of standard experimental conditions should then give results that w i l l signify the type of response governing the natural reaction to an environmental factor. Influence of Intensity Level From the experiments with light intensity i t has been demonstrated that Simocephalus has an "apparent" absolute optimum light intensity. This cannot be stated conclusively for the following reasons. The light composition of the 61. lamps used as sources of Illumination was known to vary. Simocephalus has been shown to be more sensitive to blue light than to red light in the visi b l e spectrum. As the lamps used to produce the higher light intensities trans-mitted relatively more light in the blue region of the spec-trum, part of the decrease i n the response at higher inten-s i t i e s may be due to the inhibition of the response by wave lengths between 3400 A* and 4000 £ transmitted by these lamps. It i s considered, however, that the total decrease i n re-sponse past the "optimum light intensity" i s not due to this factor alone. The most pertinent data obtained i n this re-spect i s that the response s t i l l follows the trend to an absolute optimum intensity when the source remains constant, the distance of the source from the animals being varied to produce higher light intensities. The composition of the light source would then be unchanged. Johnson and Eaymont (1939) working with Centropaees. Clarke (1930, 1932) and Dice (1914) working with Daphnia. were unable to demonstrate any absolute optimum light intens-i t y above which the primary phototactic response was inhibit-ed. Russell (1927) has suggested that the reason many plank-ton species exhibit positive phototactic respnnses i n the laboratory, where the same animals react negatively to light under natural conditions, i s the great absolute difference i n light intensity existing between the two conditions. 62. Plankton forms i n the sea may be subjected to intensities as high as 2000 metre-candles and less. Conditions of ex-perimentation in the laboratory permit only much lower i n -tensities to be used. It appears that there i s such a phen-omenon as an "absolute optimum light intensity". The problem w i l l be answered eventually when the d i f f i -culties of maintaining constant light composition over a high range of intensity levels are overcome. Rate of Rise of Intensity in a Gradient The gradients of intensity established are now compared in order to determine whether the rate of rise of light in a gradient has an effect on the response. It i s found that as the rate of rise of intensity increases, the speed of redistribution of the animals also increases. The time to reach a peak i n this redistribution i s inversely correlated with the rate of r i s e . These phenomena are independent of the absolute intensity. The curve of redistribution with increase i n rate of rise of the gradient also becomes flatten-ed at the top. By many varying means, i t has been shown that the stim-ulus required for the production of a light response i s a change i n illumination intensity. The direction of the light merely serves to orient the animal to perform i t s character-i s t i c response (Johnson, 1931 and Clarke, 1930, 1932). Clarke also discusses the effect of changes i n light intensity 63. on the phototropic response. In a carefully controlled ex-periment he was able to demonstrate that the rate at whichaa response w i l l occur i s dependent upon the absolute change i n intensity or, conversely, the rate at which the intensity values change. He distinguishes between two types of i n -tensity changes: the 'time-change' and the 'place-change1. The former i s produced by a change i n the source intensity while the animal i s stationary; the latter by a change i n the position of the animal which brings i t into a region of different intensity. These two types would not necessarily change the ultimate response, although they might influence the way i n which the response occurred. The type of inten-sity change i n the present study i s a •place-change' re-sponse. Clarke (1930), using apparatus designed to test •time-change' responses, found that Daphnia would not respond to a 'place-change' of light intensity. In his experiment, Daphnia was made to respond to a 'time-change' of intensity. The response would be a positive one, being of the secondary phototropic sign, which follows a 'time-change' of intensity. As the animal beeame adapted to the light, the primary sign would then appear and Daphnia would swim to the other end of the tube, away from the lig h t . This would involve move-ment towards a region of less intense lighting. The 'place-dhange', however, would not produce the secondary phototropic sign to cause the animal to move toward the light again. 64. In the present case the following two po s s i b i l i t i e s are pre-sent: Simocephalus responds to a 'time-change' by the turn-ing on of the light at the beginning of each test, or, i t responds to a •place-ehange' by moving up a gradient of intensity. Clarke considers the possibility of there not being a sufficiently great rate of change of intensity.for Daphnia to be stimulated by a 'place-change' of intensity. There appears to be considerable evidence that the re-sponse demonstrated for Simocephalus i s to a 'place-change' of intensity. The animals show a greater positive response as the steepness of the gradient increases and the magni-tude of the response i s not correlated with the change of intensity from darkness when the light i s turned on (Figure 22). Again, there i s no correlation between the absolute change in intensity when the light i s turned on and the time for the redistribution to reach a peak. It therefore appears certain that the response to light can occur through a 'time-change' (Clarke, 1930), or a 'place-change' (present study). Duration of Stimulation A consideration of the length of time that the animals remain attracted by the light indicates that the greater the fi n a l intensity, the shorter w i l l the time to the following redistribution be after the animals have become adapted to the light intensity at the 'top' end of the gradient. These results are contrary to the findings of Clarke (1930, 1932) 65. and D i c e (1914) f o r Daphnia . D i c e (1914) s t a t e s t h a t Daphnia i s " . . . m o r e s t r o n g l y p o s i t i v e to moderately s t r o n g l i g h t than to v e r y weak l i g h t . . . " I t i s p o s s i b l e , however, t h a t i f the r a t e o f r i s e o f i n t e n s i t y i n the g r a d i e n t o f l i g h t e x i s t i n g had been c o n s i d e r e d , i t might have been found t h a t the animals were o r i e n t i n g t o a ' p l a c e - c h a n g e 1 i n i n t e n s i t y . I f t h i s were s o , the r e a c t i o n would not then be a f u n c t i o n of the a b s o l u t e i n t e n s i t y but o f the r a t e o f change o f i n -t e n s i t y o c c u r r i n g i n the l i g h t g r a d i e n t . D i c e ' s r e s u l t s a r e , however, i n harmony w i t h H e c h t ' s h y p o t h e s i s a l t e r e d and set f o r t h i n C l a r k e (1932) concern ing the mechanism of the p h o t o t r o p i c response^ T h i s h y p o t h e s i s I s d e s c r i b e d i n the next paragraph . One of the major f a c t o r s governing the p h o t i c response i s a r e v e r s i b l e photochemical r e a c t i o n expressed as " L i g h t " S r±^r P + A "Dark" Some p h o t o c h e m i c a l l y responding substance , S , i s i n f l u e n c e d by l i g h t to produce r e l a t i v e i n c r e a s e i n the amount o f P + A . I f the l i g h t i s constant the system w i l l r e a c h e q u i l i b r i u m at the new l e v e l and an animal w i l l then be adapted to the l i g h t , a t which t ime i t s p h o t o t r o p i c s i g n r e v e r t s to the pr imary from the secondary s i g n i n a ' t ime-change ' response . I f the i n t e n s i t y change was o f a h i g h o r d e r , the time to a d a p t a t i o n , or e q u i l i b r i u m i n the system, would be r e l a t i v e l y 66. longer than i f the intensity change was of a lower order. The time difference would account for the greater shift in the system under higher stimulation in order for i t to reach equilibrium. The findings of several workers are i n agree-ment with the hypothesis. In the present study the animals were dark-adapted be-fore use and would then be expected, by the above hypothesis, to become adapted in a time period directly related to the intensity. Referring back to the section concerning the re-lationship existing between intensity and magnitude of re-sponse (Figure 18), i t i s possible that this disharmony with previous experimenter's results may be a function of light quality and not intensity. It i s possible that the increase i n blue transmission of the lights used for higher intensities increased the rate of the equilibrium shift in the photo-chemical system. If this were true, the substance S, then would be more sensitive to light waves in the blue region of the spectrum. However, as the reaction to ultra-violet light was found to produce a reversal of primary orientation, the possible differential action of blue light may be acting in another manner, and not on a photochemical system such as this. If i t were, the increase i n the rate of the shift to equilibrium would be expected to produce a state of adapt-ation sooner, but not a reversal of primary sigh. Other chem-i c a l reactions are known to act i n the photic reaction. Hecht (1927) showed that dark adaptation i n Mya involves 67. a process by which a sensitive material accumulates i n the sense c e l l . If the action of ultra-violet light were such as to render this accumulation reaction non-reversible, the animal then might become negatively phototropic even though i t s primary phototropic sign at equilibrium i n a contemp-orary photochemical system were positive. In such a case, the two systems, photochemical and chemical, might work simultaneously in an interrelated manner, or the chemical system alone would be the dominant one. In any case the end result i a a reversal i n phototropic sign. INFLUENCE OF PREADAPTATION ON ACTIVITY OF RESPONSE Comparison of the three tests made with the same light gradient (as i n Tables V, XVII and XVIII) in which the ani-mals were kept, previous to experimentation, at differing light values, shows that the nature of the response does not change but that the degree of activity increases with, preadaptation intensity. The nature of this reaction i s best explained by the process of adaptation. I f the animal i s dark-adapted before exposure to light, the reaction to the light w i l l proceed u n t i l equilibrium i s reached. At this point the animal becomes adapted to the new intensity value. If a further increase in intensity i s imposed on the animal, equilibrium w i l l again shift to a higher intensity value. The results are compatible with those for the values of ac-t i v i t y obtained for the duration of response with variation 68. of intensity, i n that the higher the preadaptation intensity, the longer i s the response held to a maximum value. This maximum value becomes constant i n the upper limits where ac-t i v i t y has reached an absolute peak. In terms of activity, the difference existing between the intensity of the pre-adaptation stimulus and the intensity existing i n the grad-ient at the point into which the animal i s introduced, w i l l produce a greater change i n equilibrium. This greater change w i l l then incite greater activity on the part of the animal to regain equilibrium under conditions of a 'place-change1 of intensity. The result i s an increase i n activity with increase i n the value of preadaptation intensity. ACTION OF ULTRA-VIOLET LIGHT While light in the visible region causes a positive phototactic response, ultra-violet causes an opposite, nega-tive response. Moore (1912) has found that ultra-violet light of wave lengths shorter than 3341 A* are specific for causing negative phototropism in Daphnia pulex. The results for Simocephalus show that this reversal of response occurs within the range of 3000 - 3500 X, probably at about 3300 £. Rose (1929) i n an extensive compilation of the literature shows that ultra-violet may attract some species while re-pelling others. As Simocephalus and Daphnia are of the same family, Daphnidae, i t might be expected that their reactions to light would be similar in fundamental respects. This i s found to be true for the response to ultra-violet l i g h t . INFLUENCE OF WAVE LENGTH ON RESPONSE TO VISIBLE LIGHT It has been demonstrated that when the animals are given a choice in a gradient of quality of illumination, migration occurs toward the region i n which the shorter wave lengths are transmitted. This occurs when the intensity of illumination i s constant throughout the gradient, for the three intensity levels at which the tests were made. Great-est attraction occurs at the lower intensities. The f i l t e r which transmitted infra-red only i s seen to produce no sig-nificant response. The number of animals reaching the blue transmission region becomes smaller as the intensity i n -creases. This agrees with the responses which occurred i n the reactions to increased intensities i n Experiments 4 to 12. As previously stated, the results i n that section were open to criticism because of the variation in light compos-it i o n of the different sources used. The lamps employed in the present tests were a l l of equal illuminating strength. It i s not considered probable" that these lamps would vary in light composition i n such a manner as to give results identical with those found in the previous section. It i s therefore possible, by ruling out variations i n quality of illumination for Experiments 4 to 12, that an absolute op-timum light intensity does occur for Simocephalus. 70. That the photopositive animals w i l l "select" a region in which the shorter wave lengths of the spectrum are trans-mitted indicates that the najsur,e of tjie illumination i s a factor to be considered. As the relative radiant power transmitted by the tungsten filament lamps i s greatest i n the red end of the spectrum and diminishes toward the blue end, the response must be correlated with wave length. The relationship which may exist with equal energy emission at various wave lengths i s a further consideration. It i s an established principle that as the frequency of radiation from a source increases (or as the wave length decreases) the kinetic energy of a photoelectron produced from a light sensitive material increases as a linear function of wave length. Therefore, the kinetic energy values capable of being produced by light f a l l i n g on a light sensitive mater-i a l in the shorter wave lengths of the visible spectrum w i l l not be a function of the absolute amounts of radiant energy produced throughout the visible spectrum. It w i l l , however, increase proportionately at a higher level as the intensity of the source i s increased. It i s therefore possible that the "attracting" value of blue light i s a function of kinetic energy value which i s i t s e l f a linear function of wave length. In the human eye the peak of the relative v i s i b i l i t y curve coincides with the region of most copious radiation, 555m>' of a black body at 5200°K. This i s the approximate tempera-ture of solar radiation after passing through the earth's 7 1 . atmosphere. This indicates the degree to which the eye has adapted i t s e l f to the source of radiation to which i t i s most frequently subjected. The crustacean eye however, ap-pears to be sensitive to the ultra-violet region, to which the human eye i s insensitive. Such a statement appears to be i n order from the resulting distribution of the animals under ultra-violet l i g h t . That the spectral sensitivity curve of the crustacean eye might be shifted to a lower wave length region than the human eye i s a f a i r assumption. The spectral sensitivity of the crustacean eye and the kinetic energy level of the wave lengths within the sensitive range may possibly combine to produce the response to ligh t . Why a reversal i n response sign occurs i n the region of 3000 -3500 1 may depend on some feature of the crustacean eye i t -self. REACTION TO GRADIENTS OF INTENSITY OF SPECIFIC WAVE LENGTH  REGIONS Where each of the regions of transmission in the proceed-ing section were combined i n one gradient of constant intens-i t y , each region i s here employed i n a gradient of constant rate of rise and constant intensity. The results give fur-ther evidence that Simocephalus i s more active, or more highly stimulated to produce the characteristic response, i n the blue region of the spectrum. The response f a l l s off to lower values on each side of this region. The response i s also 72. more erratic under increasing wave lengths toward the red end of the spectrum. As the influence of light acting as a directing factor i s decreased i n the red end of the spectrum, i t i s therefore possible that the erratic nature of the re-distribution i s simply a product of the animals wandering under the partial absence of a directing stimulus. Why some animals should show a reversal of phototropic sign in the ultra-violet has not been explained. The limit of solar ultra-violet radiation l i e s at about 2900 A*. For Simocephalus this would mean a reversal of sign, occurring over a region of about 4000 - 4500 Angstrom units. Although ultra-violet i s absorbed by water more heavily than wave lengths i n the main visible spectrum, i t would s t i l l be able to penetrate, depending on the wave length, to a depth that could influence the migration of the animals i n the normal habitat. It i s possible that the animal's peak i n spectral sensitivity being i n the blue region corresponds in some way to that colour which i s presented from skylight, which i s blue on cloudless days. Ultra-violet light might then act to compensate for the attracting power of blue light by causing the animal to cease migrating upwards as i t came close to the surface where the ultra-violet would be greatest in amount. It must be remembered, however, that a number of other factors enters into the governing of the light re-sponse • 73. RESPONSE TO COMBINED LIGHT AND TEMPERATURE GRADIENTS The reactions of the animals to individual gradients of light and of temperature have been determined. When the two factors are combined so that one gradient i s operative in opposition to the other, the resulting response of the animals i s a compromise between the action of the two fac-tors. The extremes of the temperature gradient, high at one end and low at the other, are not avoided altogether by the animals. It i s doubtful that such a steep gradient as this would be found in the normal habitat. Under normal conditions i t i s suggested that the movement of animals into a region involving such temperatures would be the result of a much more extensive migration. In this respect, the animals would be less liable to enter a ,region of limiting or lethal tem-peratures without some sort of compensating reaction occurring before the effects of those temperatures could be realized on the organism. The experimental gradient demonstrates the fundamental nature of reactions as they might naturally occur. In a gradient of light intensity at a constant tempera-ture, a characteristic distribution i s f i n a l l y attained. A large number of animals move as close to the light source (the more intense end of the light gradient) as possible. In a temperature gradient, temperature level acts i n the capacity of a directing factor by causing an aggregation at 74 . one specific temperature region. When these factors are com-bined, two possible variations i n the mechanism governing the resulting response are possible. In one case, as an animal moves toward the light i n such a manner that i t i s \ / subjected to increases i n temperature, the attracting i n -fluence of the light may diminish. Conversely, as an animal moves into a region of colder temperature, the "attraction" by the light may increase. The reversal of primary photo-tactic sign such as this has been adequately demonstrated by Clarke (1932) for Daphnia. In the other case, a variation i n temperature may have no effect on the nature of the light reaction. The magnitude of the response to light would then be governed by the limiting nature of the temperature level alone. This latter statement presents the most logical a l -though not conclusive argument for the present study. When the two forces are combined the response appears to be the resultant of the forces combined i n opposition. The magni-tude of the response to a light gradient acting i n a tempera-ture gradient i s also dependent on the light composition. The greatest response, producing a shift i n the mean aggre-gation temperature, i s associated with the presence of the shorter wave lengths of the visible spectrum. In summary, the various characteristics of temperature and light affecting Cladocera are presented to il l u s t r a t e their influence on the general response. These have been com-piled from the literature and from the results of the present study. Table XXXIV. Summary of the reactions of Cladocera to light and temper ature compiled from the literature and the present study. Factor Characteristic Response of Animal Other Relationships Authority Temperature level magnitude - dependent on metabolic rate sign of light response i s reversible from low to high temperatures Clarke (1932) Russell (1927) level length of l i f e increas-es with decrease with-in lethal^limits a differential sexual re-sponse to variations in temperature affecting the metabolic rate MacArthur & B a i l l i e (1929) level acclimation occurs within range of lethal limits response to light normal after acclimation to change i n temperature. suggested Level preadaptation to lim-i t s normally encounter-ed geographically. populations restricted to general geographical tem-perature regions. Brown (1929). Light intensity constant directing influence dependent on sign of phototropic response w i l l adapt to any intensity with time Clarke (1930) Johnson C1918) direction movement to or from source in phototaxis acts independently of d i f -ferences i n intensity Spooner "Time-change" of intensity reversal of phototropic magnitude of response, speed Johnson(1938) sign u n t i l equilibrium of response directly re- Clarke (1930) regained lated. "place-change" of intensity dependent on magnitude of change in gradient magnitude of response, speed of response directly related to an optimum point. present study Factor Characteristic Response of Animal Other Relationships Authority-Light duration of s t i - adaptation faster as possible dependent also on Light & mulation intensities increase nature of illuminating present study optimum i n -tensity (abs.) activity, response greatest possibly dependent also on nature of illuminating source. present study preadaptation summation of primary responses activity increases to new equilibrium in summated resDonse present study quality decreases from blue to red end of spectrum for Simocephalus serrulatus activity increases with i n -crease i n blue transmission present n study . ultra-violet reversal i n photo-tactic sign. reversal occurs between 3000 - 3500 A for Simoce-phalus serrulatus present study gradients i n opposition activity i s resultant of the two factors. range of potential activity values dependent on light directly related. Temper-ature main factor present study gradients i n influence of light activity decreases with present opposition with decreases with loss omission of blue study light quality of blue variable Table XXXV. Comparison of some characteristics of the light response obtained by Clarke (1932) with similar characteristics obtained in the present study. Amount of Intensity Change Speed of Duration of Intensity Previous Ex-Change posure to Lieht Duration of Previous So- Temperature journ in Darkness Clarke Present Clarke Present Clarke Present Clarke Present Clarke Present Study Study Study Study Study Threshold Amount of Reduction IR — IR DR "Short" Latent Period IND? IR "Long" Latent Period Speed of Response DR IND? IR DR Magnitude of Response DR DR DRA DR IR Duration of Response DR IND - INDEPENDENT, IR - INVERSELY RELATED, DR.- DIRECTLY RELATED 4 - TO AN OPTIMUM VALUE 78. CONCLUSIONS It i s beyond the scope of the present study to reduce the behaviour of plankton populations to fundamental compon-ent reactions. It i s hoped, however, that the findings pre-sented, whether new or not, w i l l help to focus attention on what appear to be some of the fundamental properties of light and temperature affecting the behaviour of plankton in the natural environment. It Is f e l t that these two fac-tors are the most important of those which may influence dis-tribution. That a number of different responses may occur to one isolated factor from species to species does not nec-essarily require the development of a hypothesis for each differing response. The response may be similar i n i t s method of propagation from species to species, although the nature of the response may differ within a wide range of values. From this point of view the following conclusions are drawn. The range of temperature levels within which an organ-ism i s capable of existing i s dependent upon i t s organic con-stitution. The level of temperature to which the animal i s preadapted w i l l govern i t s metabolic rate and therefore i t s potential degree of activity. When the level of temperature to which the animal was preadapted i s changed, adaptation to the new level w i l l produce a change in the metabolic rate which w i l l then increase or decrease the value of potential activity u n t i l equilibrium i s reached under the imposed change. That the preferendum temperature i s not a measure of acclimation temperature i s substantiated by the fact that the preferendum temperature appears to be much greater than the temperature range to which the animal would probably be subjected i n the natural habitat. However, as i t i s a re-producible condition and i s related to the acclimation tem-perature, i t serves as a relative starting point for the introduction of successive variables in the determination of their effects on activity. The effects of light are dependent upon the manner i n which the factor i s imposed on the animal. The response to light appears to be the result of the effect of light on a reversible photochemical system, as the response i s seen to be reversible. The response of the animal to changes of light intensity, whether i t be a change of the animal's position in a gradient of the factor, or a change i n the intensity of the factor with time, incites responses gov-erned by the hypothetical photochemical system. When the system reaches equilibrium at a new level, It becomes ad-apted to the light, and the animal proceeds then as i f i t were not subjected to the stimulus. The rate at which the intensity change i s imposed w i l l govern the qualitative and quantitative aspects of the response. Subjection of the animal to a constant source of light at one intensity value raises the value of i t s ensuing activity; thus i t must also 80. increase the metabolic rate. A fundamental principle, then, of the action of light on the animal seems to be a rise of i t s metabolic rate through i t s secondary effects on activity. The reversal of re-sponse to light of wave lengths in the ultra-violet region of the spectrum i s an interesting problem. It seems logical to suggest that the response to ultra-violet light i s a means by which the organism places i t s e l f i n such a position that i t may perform one or a number of natural functions under more optimum conditions. If an animal lives i n an environ-ment i n which i t i s constantly exposed to some measure of ultra-violet radiation, i t may have become adapted to include those effects in the pursuance of normal functions. If i t i s not constantly subjected to ultra-violet light, i t may react so as to exclude that light from influencing i t s nat-ural functions. The quality, or wave length, of the visible spectrum influences- the quantitative aspects of the response to light. The spectral sensitivity curve need not be con-stant from species to species. Fundamentally, i t may de-pend on the constituents of the photochemical system or sys-tems which enable a particular species to respond to external light stimuli. When two or more factors are combined, the resulting response w i l l be a function of the two integrated factors. The resulting response must not necessarily be similar to those of other forms because the system e l i c i t i n g the response may not be exactly alike from one individual or species to another. The qualitative and quantitative aspects of the two combined factors w i l l also govern the integrated reaction. The f i n a l response w i l l depend on the nature of the two com-bined factors and w i l l vary according to the nature of their integration. It i s a f a i r l y simple matter to show how an animal responds i n the laboratory to an external stimulus. It i s not so simple a matter to relate these responses to those occurring under natural conditions. It i s f e l t that only when the experimenter knows why a response occurs, through investigation of the processes governing i t , w i l l he be able to state with assurance the effect that each fac-tor has i n the production of the reaction to environmental stimuli. 82. SUMMARY 1) A qualitative and quantitative study of the reactions of Simocephalus serrulatus (Koch) has been made for light and temperature acting as directing factors. 2) ) Apparatus was developed for maintaining constant tem-peratures or temperature gradients and for producing various conditions of illumination. 3) The data have been treated i n such a manner as to per-mit comparison of the responses to various aspects of the external stimulus i n terms of variations from random dis-tribution and the degree of activity produced i n the response. 4) Simocephalus serrulatus was found to have a temperature preferendum of 19.13°C. when previously held at approximate-ly lf F.5°C. and put at 19°C. for 14 hours prior to experi-mentation. The value of the temperature preferendum i s the peak of a distribution having a range from 7.2°C. to 33.6°C. The preferendum i n a temperature gradient appears to be a function of the temperature to which the animal was previous-ly adapted and o.5b the rate of change of temperature in the gradient. If the gradient i s made fl a t t e r the peak of dis-tribution becomes smaller and the animals tend to spread out over the range In greater numbers. 5) Simocephalus serrulatus was found to be positively phototactic to vis i b l e light of any intensity used i n the experimentation. 83. 6) Solutions of f i l t e r e d pond water and strychnine sulphate, ethyl alcohol and HCl to produce a pH value of 3.8, did not reverse this positive response to light but made the ani-mals react indifferently to illumination. 7) The response to light i s shown to have an absolute intensity optimum. 8) The rate of rise of intensity i n a light gradient i s shown to be a) directly related to the magnitude of the response. b) inversely related to the time for the re-sponse to reach a peak value. 9) The intensity of illumination i s shown to be inversely related to the time for adaptation to occur. 10) The response to light, of animals previously held at * various intensities, shows that the magnitude of the re-sponse to light i s directly correlated with intensity of the preadaptation stimulus. 11) The time for adaptation to light intensity i s shown to be inversely correlated with the intensity of the preadaptat-ion stimulus. 12) Ultra-violet light below the region of 3000- 3500 1 i s found to be specific for producing a reversal of the posi-tive phototactic sign i n Simocephalus serrulatus. The re-versal of sign commences at approximately 3300 £. 13) Wave lengths at approximately 4000 A* i n the visib l e spectrum cause the largest positive phototactic response. 14) The magnitude to the response to light i n the region of 4000 % i s shown to be inversely correlated with intensity. 15) The interaction of light and temperature, acting as r directive factors ,in opposition to eachbther, i s found to produce a response which i s the resultant of the magnitude of the two factors operating singly. 16) A discussion i s presented of the characteristics of the fundamental reactions possibly involved i n the e l i c i t a -tion of the responses demonstrated. 85. APPENDIX 1 ) 2 ) 3) 4 ) 5) 6) 7) 8) For the interpretation of the following tables consult notes below. The distribution at zero time i s referred to as the "theoretical distribution". The distributions at subsequent time intervals are referred to as "actual distribution". Derivations of ~)£ and 0 are outlined i n the section "Method for Treatment of Raw Data" (see index). The degrees of freedom f o r single time or compartment derivations are one less than the number of cata-gories: (n-l). The degrees of freedom for the total "y*« are one less than the number of compartments times tiie number of time counts, not including zero time: (n-l) x (n ). An asterisk following a *X- e value signifies that that value and the value of 0 derived from i t show signi-ficance (i.e.) the variation from raadom distribution i s not attributable to chance alone). In computing C, N i s equal to the number of observations. For example, i n Table IV to derive Final Total C: * I 5 l t 3 3 - Q Probability level of .05 has been used to test for significance. TABLE 17. (Experiment 3 ) . Distribution of Animals in the Preferendum Temperature. No External Stimulus Applied. TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS V C 1 2 3 4 3 6 7 8 9 0 3 3 3 3 3 3 3 3 3 27 3.0 0 0 1 4 2 4 2 1 5 3 4 2 27 3 .0 4 .6 .387 2 4 2 4 2 1 5 3 3 2 26 2.8 4 .4 .374 3 3 2 4 1 2 4 2 5 1 24 2.6 5 .0 .436 4 3 2 4 1 2 3 1 6 3 25 2.7 6.0 .458 5 3 2 4 1 2 3 1 6 2 24 2.6 7.0 .458 6 3 1 4 2 1 2 3 5 4 25 2.7 5 .3 .412 COMPARTMENT TOTALS 20 11 24 9 9 22 13 2? 14 131 33.0 .424 COMPARTMENT MEANS 3.3 1.9 4.0 1-3 1.5 2£ 2J. 4.8 2.3 FINAL TOTALS V " .66 3.0 2.0 5.0 3.0 3.3 3J3 510 2.6 33.5 .424 TABLE VTII. (Experiment 4 ) . Response of Animals to a Gradieut of .023 to .122 Foot Candles. Rate of Rise of Intensity i s .16. TIME (HRS.) COMPARTMENT TIME TIME MEANS C 1 1 2 1 3 1 4 1 5 1 6 1 7 8 9 TOTALS LIGHT INTENSITY, f.c. • • 025 .031 .036 .042 .030 .064 .078 .110 .122 0 3 3 3 3 3 3 3 3 3 27 3 . 0 0 0 6 1 1 1 4 2 2 2 7 26 2.9 13.6 .583 1 6 1 1 3 2 3 1 4 5 26 2.9 9 .0 .510 2 5 2 1 3 2 4 2 4 4 27 3 . 0 4. 0 .361 3 4 2 1 3 1 4 3 4 5 27 3.0 5 . 3 .400 4 4 2 1 4 1 0 4 6 5 27 3 . 0 11.3 .548 5 3 3 3 3 1 2 3 6 3 27 3.0 4.8 .387 6 3 3 3 3 1 2 2 5 5 27 3 . 0 4.8 .387 COMPARTMENT TOTALS 31 14 11 20 12 17 17 31 34 187 52.8 .469 COMPARTMENT .. MEANS 4.4 2.0 1.6 2.9 1.7 2.4 2,4 M 5f0 FINAL TOTALS •"V1 6*0 3.61 6.b 4.6 2.6 8.6 1L0 |52.9| .469 TABLE IX. (Experiment 5). Response of Animals to a Gradieut of .010 to 1.54 Foot Candles. Rate of Rise of Intensity i s -.56. TIME (HRS.) COMPARTMENT M 4 I M M 7 1 8 I * 010 O i l .012 .016 .023! .044 J1L LIGHT INTENSITY. f.o. . 3 o 7 1.54 TIME TOTALS TIME MEANS T1-3 T 27 24 3.0 2.7 i Q . o 0 1 - I T 3 11 26 2 . 9 29.7 3oTo .728 12 25 .775 11 25 2.8 29.3 .728 IF 12 2 7 3.0 38.7 .768 4 13 26 2.9 44.3 s 10 25 2.8 28.7 .728 4 "4T 8 25 2.8 27.3 .721 36TI *5F i i 24 2.7 UK .774 12 .6*. "7F 13 24 2.7 4 4 ^ .806 12 26 2.9 42.3 .725 "8F IF 14 27 3.0 57.4 .837 15 27 3.0 63.3 .836 10| 14 11 25 2.8 58.0 .825 48^1 .812 2 T F COMPARTMENT TOTALS COMPARTMENT MEANS 0 12 24 25 40 23 10 1.47 2A 1.4 0.6 0.5 0.2 22. -2i_ 201 1.7 11.8 1^1 12. ,787 ft82..3 OS-L FINAL TOTALS " Y 1 14.8 1UD U8.0 37.0 37.3 46.7 14.0 43.0 460.6 1682.3 .781 TABLE X. (Experiment 6 ) . Response of Animals to a Gradieut of .007 to 7 .2 Foot Candles. Rate of Rise of Intensity i s . 7 7 . TIME (HRS. ) COMPARTMENT TIME TOTALS TIME MEANS C 1 1 2 1 - 3 1 4 1 5 1 b | 7 1 B I 9 LIGHT INTENSITY, f.c. . 007 ,00? .011 .013 t'Ca-7 .027 ,067 r367 7,2 0 5 3 ? 3 3 3 3 3 3 27 3 0 D * 5 U~~ 4 2~~ CT" 1 T ~ T U — 27 3 26 . 0 r?00 1 5 3 0 ? 0 0 4 3 9 27 3 22.6 .678 1* 5 3 1 2 0 0 0 6 10 27 3 3 1 . 3 .734 2? 5 l 0 3 1 0 0 5 12 27 3 4 1 . 3 t775 3 l 1 ? 0 0 0 b 11 27 3 37.} AI 5 2 1 2 0 0 0 6 11 27 3 3 6 . 6 .762 3 2 1 2 0 0 0 6 11 *7 3 3 6 . 6 .762 OS 5 4 0 0 0 .0 1 6 10 26 2 . 3 3 4 . 3 •755 8 I 2 0 0 0 0 2 6 10 26 2 .9 3 5 . 0 •755 9 5 4 0 0 0 0 2 7 8 26 2 .9 27tb t?21 k 7 3 0 0 1 2 3 2 ? 27 3 2^,3 •693 21& b 2 ? 2 2 1 5 2 2 25 2.8 7.3 .480 COMPARTMENT TOTALS 61 30 7 21 6 3 18 57 113 316 ; 361.2 .728 COMPARTMENT MEANS 5.0 2.5 0.6 1.8 0.5 0.3 1.5 4.8 9 . 4 FINAL TOTAL: y-1- 23.3 4.6 26.3 13.6 27.3 30.J8 20.0 23,9 189.0 361.8 .728 C O TABLE XI. (Experiment 7 ) . Response of Animals to a Gradieut of .007 to 7.2 Foot Candles. Rate of Rise of Intensity i s . 6 5 5 . TIME (HRS. ) COMPARTMENT TIME TIME MEANS C 1 1 2 1 3 1 41 5 1 b 1 7 1 8 1 9 TOTAL* LIGHT INTENSITY, f .0. .222 -289 t??3 .500 .631 .833 1.02 1 .32 0 3 3 3 3 3 3 3 3 ? 27 3 0 0 * 2 3 3 2 1 3 1 2 25 2.8 12.0 t566 1 2 3 2 2 2 2 2 2 10 27 3 18.6 .640 1* 2 3 ? 2 1 2 1 5 7 2o 2.9 10.3 t?43 2 2 2 3 2 2 1 2 3 ? 27 3 15.0 .600 3 2 0 4 1 4 4 2 \ 6 2b 2.9 9.0 5 t 2 1 3 2 3 4 3 7 H 27 3 8.0 .48o 4 3 1 4 1 3 2 3 1 5 23 2.6 6.0 .451 4 l 3 1 3 0 5 1 b 24 2t7 12f0 .^74 61 4 •1 3 4 2 1 3 3 6 27 3 fl 6.6 .447 It 2 2 3 3 2 1 4 2 6 25 2.8 6 . 0 .43b 2 2 3 1 4 1 3 1 4 21 2 ,3 5,3 T447 9£ 3 ? 3 1 3 3 1 0 5 22 2.4 7.0 23 7 2 4 1 1 2 2 1 4 24 2.7 11.0 .55b COMPARTMENT TOTALS 37 24 41 23 31 26 32 26 83 1 323 126.8 t?2? COMPARTMENT MEANS "V-1 2f8 8.6 1.8 3tl 1.3 1.8 10.0 2*4 6.0 2.0 i o t 3 2.4 7*0 2 T0 10.3 hi • 62.6 FINAL TOTALS 1125.7 1.529 TABLE XII. (Experiment 8 ) . Response of Animals to a Gradieut of .006 to .500 Foot Candles. Rate of Rise of Intensity i s .49 TIME (HRS. ) COMPARTMENT TIME TOTALS TIME MEANS C 1 1 2 1 3 1 4 1 5 1 6 1 7 I 8 | 9 LIGHT INTENSITY, f.c. .006 .008 .010 .013 .023 .037 .074 .174 .500 0 3 3 3 3 3 3 3 3 3 27 3 0 0 * 2 0 1 2 2 11 27 3 26.7 .707 1 3 2 1 2 2 1 3 0 13 27 3 4 0 . 0 .774 1* \ 2 1 2 l 0 3 0 14 2o 3 49 .7 .812 2 4 1 2 2 0 2 0 14 27 3 49 .3 .806 2* 3 3 0 2 3 0 2 0 14 27 3 50 .0 .806 3 3 3 0 2 3 0 2 1 13 27 3 41 . 1 .800 3 t 3 2 0 1 2 2 2 1 14 27 3 47 .3 .800 Alt 3 2 2 1 2 3 2 1 11 27 3 25 .3 t6?3 5* 2 2 3 1 2 1 3 0 13 27 3 4 0 . 0 Of- 2 2 3 1 2 0 1 1 12 24 35 .0 .768 1%. 2 3 1 2 3 1 1 2 10 25 2.8 21.3 .678 COMPARTMENT TOTALS 29 28 14 16 23 10 23 9 139 291 425.7 .775 COMPARTMENT MEANS 2.6 2 . 3 1.2 1 .4 2.1 1.0 2.0 .8 12.6 FJUX TOTALS ~Y-1 1 .3 2.3 15.0 10.3 4 . 6 19.6 4 . 6 20.6 347.3 |425.6 | .775 TABLE XIII. (Experiment 9). Response of Animals to a Gradieut of 1.1 to 36.0 Foot Candles. Rate of Rise of Intensity i s .39. TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS C 1 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 LIGHT INTENSITY, f.c. 1.1 1.1 1.1 1.2 1.4 2 .3 4.7 142 36.0 0 3 3 3 3 3 3 3 3 3 27 3 0 0 * 1 0 1 2 3 1 1 2 9 f 20 2.2 21.0 .714 1 2 l 0 0 l 0 1 - 1 12 18 2.0 41.6 4n 1£ 2 0 0 0 0 0 0 2 13 17 1.9 52.0 M 2 1 1 1 0 0 0 1 2 13 19 2.1 48.0 .849 2 t 1 0 1 0 0 0 1 3 13 19 2.1 49.3 .849 3? 0 0 1 1 0 0 1 0 13 16 1.8 52.3 •if;* 4* 0 0 2 0 0 0 0 0 13 15 1.7 54.6 .883 5ft 0 0 0 1 0 1 2 4 10 18 2.0 31.6 .800 b e 0 0 0 0 1 1 3 2 8 15 1.7 23.3 .781 1 1 1 1 0 0 2 5 5 16 1 .8 14.3 .686 COMPARTMENT TOTALS 8 3 7 5 5 3 12 21 109 173 388.0 .830 COMPARTMENT MEANS .8 .3 .7 . 5 . 5 .3 1.2 2.1 10.9 FINAL TOTALS "V1 18.0 25.0 19.0 22.0 23.6 25. 13-3 10.3 23L6 387.8 | .830 TABLE XIV. (Experiment 10). Response of Animals to a Gradieut of 1.1 to 4 8 . 6 Foot Candles. Rate of Rise of Intensity i s .422. TIME (HRS.) 1.1 JL-1 COMPARTMENT 4 1 5 1 6 1 7 I Z-TT LIGHT INTENSITY, f.o. 1.2 |1.4 1 2.0 | 2.9 1 4.3 1 9.0 24.1 4876 TIME TOTALS TIME MEMS V 0 27 "2T 1 0 i i 5*0 C 3 1 TT 4 T l T 2 TiTo" "2T T" T T2Tb" T2Tb" •2T T T T T 4^  " S T IT TT T T "2~ ToTo-12.6 IBTo 1 T .2*2 17.0 1 4 24 H 1376 1676 2 1 4.0 COMPARTMENT TOTALS 40 11 27 32 36 33 34 60 93 COMPARTMENT MEANS 2.9 3.3 . 8 26.3 1.9 8 3 2.3 12.6 2.6 4.6 1L6 2A 4.0 4.3 20. 6.6 79.0 366 L69.3 FINAL TOTALS 169.71 .565 TABLE XY. (Experiment 11). Response of Animals to a Gradieut of 1.8 to 47.7 Foot Candles. Rate of Rise of Intensity i s .36. TIME (HRS.) COMPARTMENT TIME P0TALS TIME MEANS C 1 1 2 l 3 1 4 1 5 1 6 1 7 1 8 1 9 LIGHT INTENSITY, f.o. 1.8 2 r6 ?.o l i t 7 14.4 24.1 36.0 45.0 47.7 0 3 3 3 3 3 3 3 3 3 27 3 0 0 * 3 3 1 2 3 0 6 3 6 27 3 10.6 .529 1 3 ? 2 3 1 0 5 3 7 27 3 11.3 .548 1* 4 2 1 2 1 2 4 4 7 27 3 10.0 .520 2 4 2 3 0 1 2 2 3 8 27 3 15.3 .600 2* 4 3 0 0 3 2 2 5 8 27 3 ib fo .616 3 4 1 2 1 1 0 2 5 11 27 3 -Pi 4 4 1 2 1 1 1 3 4 10 27 3 2£ f6 .678 5 2 3 2 1 2 1 2 4 9 2o 2.9 16.3 .625 5 2 1 ' 2 1 1 2 3 4 7 23 2.6 10.6 .^6 7 2 2 2 0 1 1 3 5 6 24 2.7 12.3 9 1 1 1 1 3 2 4 5 5 23 2.6 8.6 .520 COMPARTMENT TOTALS 33 22 18 12 18 13 38 47 84 285 165.5 .608 COMPARTMENT MEANS 3 2 1.6 1.1 1.6 1.2 3.5 4.3 7.6 FJHSL TOTALS 4.0 6.3 9.0 16.3 9.6 14.6 7.6 8.0 89.6 [L65.0 .608 TABLE XVI. (Experiment i i i ) . Response o f Animals t o a Gradieut o f 9.0 t o 60.1 Foot Candles. Rate o f R i s e o f I n t e n s i t y i s .21. TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS C J- 1 2 1 3 1 - 4 - 1 5 1 6 1 7 1 8 1 9 LIGHT INTENSITY, f . e . 9.0 10.8 14.4 19.8 27.0 34.2 4 5 . 0 54.0 60.1 0 4 2 ? 3 — 3 3 27 3 0 0 3 l 4 2 2 1 8 27 3 12.6 .566 1 2 1 1 2 4 2 1 2 8 23 2.6 14 . 0 .S16 1* 3 2 0 1 3 5 1 6 6 27 3 13.3 .574 2 5 1 0 1 5 2 1 5 7 27 3 16.£ .616 2* 5 . 1 0 1 4 3 1 3 9 27 3 20.6 .656 3 5 1 0 0 7 1 1 4 8 27 3 25 . 3 •j>?3 5 t 5 1 0 0 2 6 1 5 6 2b 2.9 17.6 .632 2 1 2 2 - l 2 b 6 27 3 11.3 .548 bS 5 2 0 0 2 3 6 4 5 27 3 1216 .566 7s 5 2 0 0 2 6 2 3 5 25 2.8 12.6 .583 COMPARTMENT TOTALS 44 15 5 8 35 31 18 39 68 263 156,5 .608 COMPARTMENT MEANS 4.4 1.3 .5 .8 3.5 3 t i 1.8 3t? 6 f 8 FTNJL, TOTALS 10,0 8.3 23.3 18.0 9.0 3X0 120 U .0 54.0- 1156 .6| .608 TABLE XVTI. (Experiment 1 3 ) . Response o f Animals t o a G r a d i e n t o f .007 to 7.2 Foot Candles When P r e v i o u s l y H e l d F o r 17& Hours at 7.2 Foot C a n d l e s . Rate o f R i s e o f I n t e n s i t y As I n Experiment 6. TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS C 1 1 2 3 ! 4 - 1 5 b 7 1 8 9 LIGHT. INTENSITY, f . c . .Q07 ,00? .011 .013 .017 ,027 .067 .376 7,2 0 3 3 3 3 3 3 3 3 - 3 27 3 0 0 2 3 i u 0 1 b 2 1J> 27 3 57.3 .825 1 2 2 2 1 1 0 0 lb 27 3 bb.O .643 1* 1 \ 5 3 0 0 0 0 16 27 3 71,3 •8?4 Zf 1 4 0 4 0 0 0 1 16 2b 2.9 ,834 3£ • 2 0 3 3 1 0 0 1 16 26 2.9 68,3 ,84? 4? 2 1 l 2 0 0 0 0 20 26 2.9 M M .900 5 ? 1 3 2 0 1 0 1 0 18 26 2.? 88.3 ,878 ll 2 1 1 2 0 0 0 0 20 26 2,9 HI. 7 .900 12.1 1 3 2 0 0 0 0 0 18 24 2,7 91,7 •88* 2b 0 b 1 1 0 1 0 0 18 27 •3 94.0 .883 COMPARTMENT TOTALS 14 2b 18 17 3 3 4 4 173 262 832.0 .872 COMPARTMENT MEANS 14 2.6 1 .8 1.7 . 3 . 3 .4 .4 17.3 FINAL TOTALS 10.0 10.7 IL7 25.0 25.0 25.3 24.0 69JL0 832.0 1 .872 TABLE XVTII. (Experiment 14). Response o f Animals to a Gradient of .007 to 7.2 Foot Candles When Previously Held For 15| Hours at 13.5 Foot Candles. Rate of Rise of Intensity As In Experiment 6. TIME (HRS.) COMPARTMENT TIME TOTALS TIME UfEANS V C 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 LIGHT INTENSITY, f . c . .007 .00? .011 .013 .017 .027 .067 3,67 7.2 0 ? 3 3 3 3 3 3 3 3 27 3 0 0 1 t a 0 3 3 1 3 0 0 1 16 27 3 68 .0 .84? 1 0 3 4 0 0 0 . 1 0 19 27 3 102.0 .872 1* 1 0 3 0 2 1 0 0 20 27 3 111.3 2 0 2 3 0 1 1 0 0 20 27 3 111.3 .8?4 2* 0 1 2 1 0 1 0 1 20 2o 2.? 111.0 .900 3 0 2 1 1 0 0 1 0 21 26 2,? 124.3 .?11 3* 0 1 2 1 0 0 1 0 21 26 2.9 124.3 .?11 4± 0 2 1 1 0 0 1 0 21 26 2.? 124.3 .?11 5& 0 2 1 1 0 0 1 0 21 26 2.? 124.3 .911 & 0 3 1 0 0 0 1 0 21 26 2,? 125,7 .911-0 2 2 1 0 0 1 1 19 26 2.? 99.0 .889 10& 0 0 1 1 0 0 1 2 21 26 2,? 124 t3 .911 14£ 0 3 0 0 1 0 1 0 21 26 125.7 •911 23* 0 2 0 0 0 0 1 0 22 25 M 140.0 .?22 29* 0 0 2 0 0 0 1 0 22 25 2.8 140. .?22 33* 0 1 2 1 0 0 0 1 20 25 112,7 ,906 35i 0 1 2 1 0 0 0 0 21 25 2,8 126.0 .911 COMPARTMENT TOTALS 1 28 30 10 7 3 11 6 346 442 1994.2 .906 COMPARTMENT MEANS .06 49.3 1.6 16.3 l t 8 15.0 .6 34.3 42. I f : .6 32,7 ,4 41.7 20.4 1717.0 FINAL TOTALS |l??4t31 f 906 TABLE XIX. (Experiment 15)-. • Nature of the Photic Response to Ultraviolet Light TIME COMPARTMENT TIME TIME (HRS.) 1 1 2 1 3 1 4 5 1 6 1 7 8 1 9 TOTALS MEANS C HIGH ULTRAVIOLET RADIATION LOW 0 6 6 6 6 6 6 6 6 6 54 6 0 0 1 / 1 2 3 3 4 8 5 6 6 8 1 1 5 4 6 9 . 3 . 3 8 7 1 / 4 2 2 1 3 2 3 4 1 0 27 5 4 6 92.0 794 1 / 2 3 2 2 4 3 0 7 7 26 54 6 82 .0 .768 3 / 4 1 2 0 2 0 0 2 5 42 54 6 246.3 , 906 1 3 0 0 1 0 2 3 2 43 5 4 258.7 . 9 1 1 i i 3 1 1 1 1 2 0 2 4 3 54 6 257.7 .911 COMPARTMENT TOTALS 1 5 1 0 8 1 9 . 1 1 1 3 22 34 1 9 2 3 2 4 946.0 . 8 6 0 COMPARTMENT MEANS 2 . 5 ; 1 . 7 1 . 3 3 . 2 1 . 8 ' 2 . 2 3 . 7 5 . 7 3 2 . 0 FINAL TOMS >^  1 2 . 8 19.7 23.7 13.8 2}.5 18.8 11.0 9 . 0 8 1 6 . 7 946.0 .860 C . 6 7 8 .812 ,866 648 ,806 .768 .574 . 4 5 8 . 8 4 9 TABLE XX. (Experiment 1 6 ) . Response to Wave-Length Regions in a Graded Series. The Catagories Under "Lamp Transmission at 2.7 f.o." Refer to the Transmitted Light; None, Total, and That Through the F i l t e r s . Light Intensity for Each Compart-ment i s 2.7 f.c. TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS C 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 LAMP TRANSMISSION AT f.o. None Total 3850 3387 3384 3482 2424, 2408 2540 0 6 6 6 6 6 6 6 M 6 54 6 0 0 * 3 7 12 7 6 5 2 4 3 49; 5.4 12.8 .458 1 4 8 11 5 8 5 2 2 1 46 5.1 16.0 .510 2 3 14 13 3 4 4 3 2 3 49 5.4 28.8 .608 3 3 12 11 3 3 4 1 2 3 44 4.9 22.3 .583 4 3 14 13 1 4 4 2 3 2 46 5.1 32.7 .648 5 3 15 11 3 5 3 2 4 48 5.3 28.3 .608 7t 4 21 9 9 5 1 : 0 3 1 53 5.9 57.2 .721 81 3 20 14 7 3 3 0 l 2 53 5.9 60.8 .728 9 ? 3 1 7 19 7 3 2 0 1 2 54 67.0 .741 20* 3 18 19 7 2 0 2 l 2 54 6 72.0 .755 COMPARTMENT TOTALS 34 146 132 52 43 31 14 21 496 397.9 .671 COMPARTMENT MEANS 3.4 14.6 13.2 5.2 4.3 3.1 ' 1.4 2.3 21 FINAL r. TOTALS > - 12.0 156.0 303.3 11.0 9.5 18.2 37.0 24.8 26.2 398.O. .671 C .510 .721 .663 .412 .341 .608 .854 .721 .748 v O v O TABLE XXI. (Experiment 17). Response to Wave-Length Regions in a Graded Series. Light Intensity for Each Compartment i s 5.4 Foot Candles. (See Explanation for Table XX). TIME (HRS.) COMPARTMENT TIME TOTALS TIME MEANS C 1 1 2 1 3 1 4 1 5 1 6 1 1 I 8 | 9 LAMP TRANSMISSION AT 5.4 f.c. None Total 3830 3387 3384 3482 2424 2408 2540 0 6 6 6 6 6 r 9 54 6 6"""" •"0" * 2 9 ? 6 6 3 5 4 49 5.4 8t2 .374 1 3 8 n ? 4 4 \ 4 54 b 10.0 .400 2 5 14 10 7 5 4 3 4 54 6 19.3 • ?10 3 7 10 12 0 4 3 2 5 ? 54 6 14.0 4 o 10 12 6 4 2 4 5 3 54 6 13,0 ,436 5 6 10 10 5 5 2 4 5 5 52 5.8 .387 u 6 10 8 0 5 4 1 5 6 51 5'1 ST5 .387 4 13 9 6 4 5 1 5 5 52 5.8 15,7 .458 10* 5 14 7 5 5 4 1 . 3 6 50 5.6 17.7 .510 19* 5 14 5 4 6 5 2 5 7 53 5.9 14.8 .469 COMPARTMENT TOTALS 49 112 93 60 48 36 27 44 54 523 330.5 .447 COMPARTMENT MEANS 4.9 11.2 9.3 6.0 4.8 3.6 2.7 4.4 5.4 PINAL TOTAIS 5.b 53.0 25.6 2.7 3.3 .11.3 22.2 5.3 1.7 330.7 I .447 C .316 .366 .469 .200 .243 .141 .671 .316 A73 Table XXII (Experiment 18) Response to wave-length regions in a graded series. Light intensity for each compartment is 18 f, c. (See explanation for Table XX). COMPARTMENT lime Time Means C TIME (Hrs.) 1 2 3 4 5 6 7 | 8 9 Totals Effective Lamp Transmission ai 18 f' . c None Total 3850 3387 3384 3482 2424 2408 2540 0 6 6 6 6 6 6 6 6 6 54 6 0 0 1 5 9 10 8 5 7 4 6 0 54 6 12.0 .424 1 4 4 13 7 2 7 1 7 1 46 5.1 21.0X .557 2 1 11 14 8 3 4 2 5 0 48 5.3 30.7X .625 3 1 15 10 3 7 3 8 2 53 5.9 27.5X .583 4 1 11 12 7 4 7 1 8 2 53 5.9 22.8X .548 5 1 6 14 7 4 7 2 9 2 52 5.8 22.7X .548 7 1 13 9 6 6 10 2 5 2 54 6 22.0X .539 9 1 11 10 6 6 5 6 2 51 > 7 14.5 .469 11 ',2 12 7 4 7 7 4 8 2 53 5.9 13.8 .447 Compt. Totals 17 92 99 55 40 62 24 62 1 3 1 464 187.0X .539 Compt. Means 1.9 10.2 11.0 6.1 4.4 6.9 2.7 6.9 1.4 xFinal Totals > l 28?5 4^ .3 45*2 3.9 7.3 4.3 19?3 4.0 32.? C .283 .557 .557 .265 .387 .245 .67] . .245 .843 187.0X .539 Table XXIII (Experiment 19) Response i n a gradient of light intensity from 0.06 to .55 foot-candles. No f i l t e r TIME COMPARTMENT Time Totals Time Means c (Hrs.) 1 2 3 5 6 7 8 9 Light Intensity - No F i l t e r 0 0.06 0.08 .09 .12 .17 .21 .29 .42 .55 6 6 6 6 6 6 6 6. 6 • 54 6 0 0 i A 6 7 2 3 2 4 5 21 54 6 46.0X .678 1 6 A 8 2 1 4 6 19 54. 6 37.7X .640 2 6 6 5 5 3 3 1 4 21 54 6 45.7* .678 3 A 6 5 7 2 3 2 6 19 54 6 36.0X .632 4 5 5 6 7 3 3 1 7 17 54 6 28.0X .583 5 5 A 7 7 2 2 8 15 54 6 21.3X .529 7 7 5 5 5 4 3 1 6 18 54 6 "31.0X .600 8 8 6 5 3 8 2 2 7 12 53 5.9 14.5 .458 9 6 9 3 8 2 2 8 11 53 5.9 14.5 .458 10 8 6 2 3 10 1 4 9 11 . 54 6 18,0X .500 Compt. Totals 59 57 50 50 47 22 23 66 164 538 • 292.7 .592 Compt. Means 5.9 5.7 5.0 5.0 4.7 2.2 2.3 6.6 16.4 Final Totals X 3.2 3.2 5.0 8.7 15.2 25.0X 25.2* 4.0 203.3: 292.'8 .5921 "' Table XXIV (Experiment 20) Response i n a gradient of light intensity as in Table XXIII. F i l t e r § 3387. TIME COMPARTMENT Time Time (Hrs.) 1 2 3 4 5 6 7 8 e Totals Means c Light Intensity # 3387 F i l t e r .06 .07 .08 .15 .20 .28 .40 .55 0 6 6 6 6. 6 6 6 6 6 54 6 0 0 6 6 1 4 5 3 9 5 13 52 5.8 16.3X .490 I 6 3 3 3 2 3 5 10 17 52 5.8 31.7X .616 2 6 5 2 1 1 0 2 5 32 54 6 132.7X .843 3' 6. 5 3 1 0 1 1 7 30 54 6 116.3X .825 4 5 6 2 0 2 2 1 9 27 54 N6 93.3X .794 5 5 6 2 0 1 2 2 9 27 54 6 93.3X .794 7 4 7 2 0 1 0 1 11 24 50 5.6 82.0X .787 9 A 7 2 0 1 1 1 14 22 52 5.8 75.3X .768 Compt. Totalc 42 45 17 9 13 12 22 70 192 422 640.9X .775 Compt. Means 5.3 9.0 2.1 1.1 1.6 1.5 2.8 8.8 24.0 Final Totals? 1.7 2.2 20.53 28.2 X 28.7X 4 21.0X480.7X 1 1 - 6a. 2 x .775 Table XXV (Experiment 21) Response i n a gradient of light intensity as i n Table XXIII. F i l t e r #3384. TIME COMPARTMENT Time Time (Hrs.) 1 2 3 4 5 6 7 8 9 Totals Means C Light Intensity (f.c.) # 3384 F i l t e r .04 .06 .07 .09 .14 .19 .28 . a .55 0 6 6 6 6 6 6 6 6 6 54 6 0 0 8 6 5 3 5 8 4 5 8 52 5.8 4.7 .283 1 6 5 4 1 5 5 7 7 14 54 6 16.3X .447 2 0 5 2 10 4 5 5 8 13 52 5.8 21.3X .539 4 3 3 3 7 3 3 4 10 18 54 6 35.0X .625 6 3 3 5 5 2 3 5 15 12 53 5.9 27.2* .583 7 1 1 9 3 3 6 6 8 13 50 5.6 21.7X .548 8 1 1 7 4 4 4 6 10 14 51 5.7 23.8X .566 9 1 4 4 4 1 2 10 9 15 50 5.6 30.7X .616 Compt. Totals 23 28 r . 39 37 27 36 47 72 107 416 180.7X .548 Compt. Means 2.9* 3.5 4.9 4.6 3.4 4.5 5.9 9.0X X 13.4 ^Final Totals >- 22.2 12.3 7.5 11.5 11.5 7.3 4.5 22.0 81.7 180.5X .548 Table XXVI (Experiment 22) Response i n a gradient of light intensity as i n Table XXIII F i l t e r #34-82 TTMK COMPARTMENT Time Time (Hrs.) 1 2 3 4 5 6 7 8 9 Totals Means V C Intensity (f. c.) F i l l e r # 3482 .03 . 0 4 .05 .07 .10 .15 .23 .37 .55 0 6 6 6 6 6 6 6 6 6 54 6 0 0 i 5 9 8 9 4 3 2 5 7 52 5.8 9.0 .387 I 8 4 5 7 4 5 6 2 8 49 5.4 5.8 .332 2 4 3 5 10 9 8 6 , 5 4 54 6 8.0 .361 3 6 9 5 0 3 4 4 7 15 53 5.9 24 .2 A .557 4 6 13 2 0 7 2 3 8 9 50 5.6 23 .3 X .566 5 11 8 4 5 1 3 3 5 14 54 6 23.7* . .557 7 6 3 4 5 3 1 6 9 16 53 5.9 26.2A .574 9 5 6 2 8 2 3 3 10 13 52 5.8 2 0 . 0 X .529 10 5 4 6 4 5 5 1 7 17 . 54. 6 26 .3 X .574 11 6 3 . 5 5 3 3 6 7 16 54 6 21.7* .539 12 10 6 2 3 4 4 7 3 15 54 6 23.3* .548 24 4 1 6 4 4 0 8 10 15 52 5.8 29.0X .591 Compt. Totale i 76 69 54 60 49 41 55 78 149 631 240.5 X .529 Compt. Means 6.3 5.8 4.5 5.0 4.1 3.4 4.6 6.5 12.4 ^ i n a l r totals 9.3 X 21.7 10.7 2 0 x 3 15.8 21.2 12.8^ 12.1 115.8 X 2 4 0 . 3 X .529 Table XXVII (Experiment 23) Response i n a gradient of light intensity as i n Table XXIII F i l t e r #2424 COMPARTMENT Time Totals Time Means C TIME (Hrs.) 1 2 3 4 . 5 6 7 8 9 Intensity (f. c.) # 2424 F i l t e r .01 .02 .02 .03 .06 .09 .15 .29 .55 0 6 6 6 6 6 6 6 6 6 54 6 0 0 £ 7 4 4 4 7 5 5 10 8 .. 54 6 6,0 .316 1 8 5 6 3 4 1 5 6 10 48 5.3 10.0 .412 2 14 6 2 3 2 3 4 7 13 54 6 28.0X .583 3 6 6 7 6 2 5 7 4 11 54 6 8.0 .361 4 9 8 7 1 2 2 3 4 12 48 5.3 20.0X .539 5 7 6 4 7 1 4 7 2 11 49 5.4 12.8 .458 8 6 7 6 6 3 4 6 3 13 54 6 12.0 .424 9 10 4 6 5 4 6 5 5 8 53 5.9 5.2 .300 10 6 4 4 6 3 7 7 7 10 54 6 6.0 .316 11 7 2 4 3 4 7 6 4 12 49 5.4 12.5 .447 21 6 5 3 5 4 2 2 9 13 49 5.4 17.5X .510 £pmpt. Totali 3 86 57 53 49 36 46 57 61 121 566 138.0X .447 Compt. Means 7.8 5.3 4.8 4.5 3.3 4.2 5.3 5.5 11 x Final To tals 16.0 5.8 7.2 9.8 18.0 13.0 5.8 10.8 51.5 137.9* .447 Table XXVIII (Experiment 24) Response in a gradient of light intensity as i n Table XXIII F i l t e r #2408 TREAT. TIME (Hrs.) COMPARTMENT Time Time 1 1 2 3 4 5 6 7 8 9 Totals Means C ' Intensity (f. c.) # 2408 F i l t e r .01 .02 .02 .03 .05 .09 .16 .23 .55 » 0 6 6 6 6 6 6 6 6 6 54 6 0 0 4 5 4 4 8 5 3 6 10 49 5.4 7.2 .346 1 3 4 6 7 7 4 6 3 10 50 5.6 7.3 .361 2 12 7 7 1 4 2 4 4 13 - 54 6 23.3X .548 3 10 9 ' 11 2 4 4 3 3 5 51 • 5.7 15.5X .480 4 9 6 9 6 5 5 3 2 7 52 5.8 7.7 .361 5 10 7 6 9 8 1 1 2 7 51 5.7 16.2X .490 6 9 6 7 9 4 4 1 4 7 51 5.7 9.5 .400 8 5 9 9 10 5 6 3 1 6 54 6 11.7~~~ ~rz24~~" 10 7 8 5 8 3 3 6 5 5 50 5.6 5.0 .300 11 9 7 6 7 1 7 0 6 7 50 5.6 12.3 .490 Compt. Totals 7o 68 70 63 49 41 30 36 77 512 115.7A ,424 Compt. Means 7.8 6.8 7.0 6.3 4.9 4.1 3.0 3.6 7.7 x Final Totals V 18.3X 5.0 8.3 14.2 9.5 10; 8 21.0 14.0 14;5 115.6X .424 Table XXIX (Experiment 25) Response to opposing gradients of light and temperature. Control experiment; no li g h t . Temperature values i n each compartment for tables XXIX to XXXII are li s t e d i n table XXXIII. The li g h t gradients are those of the proceeding set of experiments (Tables XXIII to XXVIII, Appendix) TIME COMPARTMENT Time Totals Time Means C (Hrs.) 0 1 : 2 | $ t A t 5 i 6 s 7 ; 8 ' i 9 : Light Intensity f. c. 0.0 6 6 6 6 6 6 6 6 6 54 6 0 0 7 5 0 1 6 6 6 8 14 53 5.9 10. 2X .592 * 7 5 0 2 6 4 7 9 14 54 6 9.5X .575 1 7 5 0 1 7 8 8 12 53 5.9 12.5X .608 2 7 5 0 0 1 8 10 6 12 49 5.4 19.5X .714 3 8 5 0 0 3 10 12 7 6 51 5.7 22.2X .686 4 7 7 0 1 7 7 7 8 10 54 6 10.7X .574 6 7 7 2 1 2 7 7 4 12 49 5.4 9.8X .583 7 7 7 2 3 8 3 9 3 12 54 6 7.8* .490 8 7 7 2 2 6 8 7 4 11 54 6 6.2ir .447 Compt. Totals 64 53 6 11 43 60 74 57 103 471 108.4X .600 Compt. Means 7.1 5.9 .7 1.2 4.7 6.7 8.2 6.3 11.4 Final Totals 2.0 1.5 9.8 6.7 12.; 6.5 52.2 C .938 .872J ,A2l .316 .374 108.3X .600 Table XXX (Experiment 26) Response to opposing gradients of light and temperature. Light operating with no f i l t e r (See explanation of Table XXIX) TIME (Hrs.) COMPARTMEM T Time Time 1 2 3 4 5 6 7 8 9 Totals Compts. Means Compts. c Light Intensity (f.c.) No F i Iter .55 .42 .29 .21 .17 .12 .09 .08 .06 3-7 3-7 0 0 6 6 6 6 6 6 6 6 30 6 0 0 £ 6 6 1 3 6 9 7 8 7 26 5.2 7.3 .469 i 6 6 1 3 6 9 7 8 6 26 5.2 7.3 .469 I 6 6 0 2 11 5 7 10 7 25 5.0 13.2* .592x 2 6 6 1 4 7 8 8 6 8 28 5.6 6.3 .424 3 6 6 2 6 5 5 9 9 6 - 27 5.4 4.5 .374 5 6 6 2 6 9 2 7 9 7 26 5.2 7.0 .458 6 6 7 1 8 6 3 6 6 7 24 4.8 6.3 • .458 7 6 7 2 7 •9 4 7 5 7 29 5.8 5.2 .387 8 6 7 2 9 8 3 6 7 6 28 5.6 6.3 .424 Compt. Totals 54 57 12 48 67 48 64 68 61 239 63.4X .458 Compt. Means 6.0 6.3 1.3 5.3 7.4 5.3 6.0 7.6 6.8 Final Totals 33.3 8.7 8.2 10.3 3.0 63.5X C .854 .387 .332 .141 .211 .458 Table XXXI(Experiment 27) Response to opposing gradients of light and temperature. Light operating with f i l t e r # 3384 (See explanation of Table XXIX) TIME (Hrs.) COMPARTMENT Time Total 3-7 i n c l . Time Mean 3-7 i n c l . 3-7 i n c l . C 3-7 i n c l . 1 2 3 4 5 6 7 8 9 Light I itensil # (f.c .) F l i t e r # 3384 .55 .41 ; .28 .19 .14 .09 .07 .06 .04 0 6 6 6 6 6 6 6 6 6 30 6 0 0 i 6 8 2 6 6 8 6 3 9 28 5.6 3.3 .332 4 ' 6 9 2 4 6 7 6 3 8 25 5.0 3.5 .346 I 6 9 1 4 4 7 7 5 8 23 4.6 5.8 .447 2 7 10 2 3 4 6 5 7 8 20 4.0 5.0 .447 4 7 11 2 3 2 6 7 5 10 20 4.0 7.0 .510 5 7 13 2 3 5 4 2 7 11 16 3.2 7.7 .566 6 7 13 3 2 5 6 1 6 11 17 3.4 8.5 .574 7 7 14 4 2 3 2 7 4 11 18 3.6 7.7 .548 8 7 14 4 5 1 2 6 4 11 18 3.6 7.8 .548 9 7 14 4 4 5 3 2 3 10 18 3.6 5.7 .490 COMPT. TOTAL 67 115 26 36 41 51 49 47 97 203 62.0 .480 COMPT. MEAN 6.7 11.5 2.6 3.6 4.1 5.1 4.9 4.7 9.7 Final Totals 3-7 i n c l - -1 " " X 21.0 12.0 10.2 8.5 10.2 - - IuUtl 61.9 C 3-7 i n c l . .671 .500 .447 .374 .412 1 & .480 Table XXXII (Experiment 28) Response to opposing gradients of light and temperature. Light operating with f i l t e r #2408 TIME (Hrs/ COMPARTMENT Time Totals Comp. 3-7 i n c l . Time Mean Comp 3-7 i n c l . 3-7 i n c l . C 3-7 i n c l . 1 2 3 4 5 6 7 8 9-(f.c) Light Inte nsity, F i l t e r # 2408 .55 .23 .16 .091 .05 .03 .02 .02 .01 0 fr" 6 6 6 6 6 6 6 " 6 ! 30 6 0 0 i 6 9 3 2 4 12 5 9 1 26 5.2 11.0X .548 £ 6": 9 : : 3 3 3 14 4 9 1 27 5.4 15.8X .608 I 6: 9" 3 2 2 16 2 9 3 25 5.0 26.2X .714 2 6*' 9': 3 2 3 12 7 7 3 27 5.4 11.8X .548 3 6;r 9'~ 3 2 4 10 8 6 6 27 5.4 8.2X .480 4 6;r 9>- 4 1 2 11 7 7 5 26 5.2 10.4X .539 6 6' 9" 3 1 3 12 8 7 5 27 5.4 13.8* .583 7 6- 9A 3 2 3 11 8 7 5 27 5.4 10.5X .529 8 6>: 9': 4 1 3 12 9 5 5 29 5.8 13.8* .566 8f t> 9' 4 1 2 11 10 3 5 29 5.8 13. ^ .557 Comp. Total 60 90 33 17 31 121 68 69 39 270 134.7X .574 Comp. Mean 6 9 3.3 1.7 3.1 12.1 6.8 6.9 3.9 Final Totals V3-7 i n c l - - 12.5 X 31.5 14.5 66.5 10.0 - - 135.0X 9-7 i n c l - - .520 .806 .566 .591 .360 - - .574 112. Table XXXIII Temperature gradient maintained for experiments 25 to 28 i n which ligh t and temperature grad-ients were set up i n opposition. | TEMPERATURE READING IN OUTER THIRD OF EACH COMPARTMENT (°C) i 1 » 2 I 3 i 4 < * J * X 5 j ,6 , 7 I s , 9 • • • • ! 35.8 ! 35.8 \ 31.8 '* 26.0 ' 1 • § 1 • • • ' 1 • # • i ! 35.8 * 33.8 | 28.2 * 23.9 ' > 5 » * t : : : 23.4 ! 20.2 • f 22.0 | 18.2 • • ; i 7 . i : i2.o ! 8.3 • • : t ' 15.0 ; 9.6 ; 7.4 • i 113. LITERATUBE CITED American Instrument Company 1945 - L o l a g e l e c t r i c hea ters and c o n t r o l s * B u l l . 2075* American Instrument C o . , S i l v e r S p r i n g , Md. B i r g e , E . A . B r e t t , J . R . Brown, L . A . 1918 - The water f l e a s ( C l a d o c e r a ) . Chapter X X I I , i n Ward. H . 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