CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE MUSEUM OF 

 COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. E. L. Mark, Director. No. 192. 



THE EFFECT OF TEMPERATURE ON THE MIGRA- 

 TION OF THE RETINAL PIGMENT IN DECAPOD 

 CRUSTACEANS 



BY 



EDGAR DAVIDSON CONGDON 



With Seven Figures 



I INTRODUCTION 



The last (ew decades have witnessed a gradual accumulation 

 of knowledge concerning photomechanical changes in the retinal 

 pigment of vertebrates, cephalopods and arthropods. It has 

 also been shown that light influences the melanophores of the 

 reptile skin much as it does the retinal pigment cells. The effects 

 of temperature upon the pigment migration of the melanophores, 

 especially in Anolis and Phrynosoma, have been discussed recently 

 by Parker ('06). Only two reports of the effects of temperature 

 on retinal pigment have appeared and these both refer to the frog. 

 Kiihne ('79, p. 334) stated that in frogs which were subjected to 

 low temperature in darkness, the retinal pigment extended farther 

 toward the light between the cones than it did in those which had 

 been subjected to high temperature in the dark. Herzog ('05) 

 subsequently investigated this subject at greater length. He 

 agreed with Kiihne that below i8°C. any decrease of temperature 

 causes a distal migration of pigment and any increase, a proximal 

 one. Above 18° C. he believed the result was the reverse. 



It was suggested to me by Prof. G. H. Parker that the decapod 

 crustaceans would be favorable objects for the study of the influ- 

 ence of temperature upon pigment migration because of the 

 marked photomechanical changes often found in their eyes. The 

 prawn, Palaemonetes vulgaris Stimp., and the crayfish, Cambarus 

 bartonii Gir., were chosen as being easily obtainable species whose 

 photomechanical reactions were well known. The conditions 

 found in Palaemonetes will be considered first. 



The Journal of Experimental Zoology, vol. iv, no. 4. 



