26 Papers from the Marine Biological Laboratory at Tortugas. 



stress on the stimulation of the eye by light, but also finds that toxic sub- 

 stances and to some extent electric shocks may bring about color change. 

 In a later paper (1876) he discusses in particular the influence of the back- 

 ground on color change. According to Fritz Miiller (1883) alarm causes 

 the color of the male of a Brazilian species of Gclasimiis to change, and this 

 is the only observation I know of on any brachyuran. Temperature does 

 not seem to be a factor in color change according to the above investigators, 

 but Jourdain (1878) working on Nika editlis finds that heat aft'ects the 

 color. Not only has he observed that low temperature causes a blanching, 

 but he also tells us that stimulation of the eye by light and internal stimuli 

 are factors in color change. The only other observations on Crustacea in 

 which temperature is said to play a part in the color changes are those of 

 Gamble and Keeble (1900). These investigators find that the color of 

 Hippolyte varians is afifected by ether or the recovery from its effect, by 

 electrical shocks, by cold, and by light stimuli through the eyes. In Anolis, 

 according to Carlton (1903), the green state is brought about by darkness, 

 withdrawal of circulation, and possibly the cutting of nerves. Specimens in 

 narcosis from ether, those treated with nicotine, and those which are dead, 

 are green in color. Carlton believes that the green state represents the resting 

 condition of the melanophores and the state to which they return when they no 

 longer receive stimuli. This green state seems to correspond to the blanched 

 condition of Ocypoda. being brought about by some of the same factors. 



The crustacean literature does not seem to afiford any extensive investi- 

 gations of color changes in land-crabs such as have been made in the 

 case of the lizard, although Gamble and Keeble (1900, 1904) have published 

 two papers which promise to be the beginning of a very thorough study. It 

 is of considerable interest, I think, to find that the results of my work on 

 Ocypoda which lives under much the same conditions as Anolis caro- 

 linensis, worked on by Parker and Starratt (1904), and especially Phryno- 

 soma blainvillei, studied by Parker (1906) agree in many respects with the 

 results obtained by these two investigators. 



The experiments so far performed yield no results which would indi- 

 cate that color environment or nervous condition are responsible for changes 

 in color observed through the carapace of Ocypoda ; nor does the immersion 

 in water seem to be a factor, except in so far as the temperature of the water 

 is concerned. Changes in the intensity of light and variations in tempera- 

 ture are undoubtedly the main stimuli, if not the only ones, which bring about 

 the proximal migration of pigment resulting in a dark color-pattern or the 

 distal migration resulting in a disappearance of the color-pattern. 



In the absence of light when the temperature is anywhere between 22 

 C. and 45 C, and undoubtedly when it is lower or even higher, a light 

 coloration occurs. 



Generally in difl:use light, and even direct sunlight, a dark coloration ap- 

 pears, provided the temperature is not too high. 



