62 KANSAS UNIVERSITY SCIENCE BULLETIN. 



torn, and of different colors in other places. An exception to 

 this was found in those of a red color. These were found en- 

 tirely in the shallow water in small streams, and the writer 

 concludes from this, and from experiments in which crayfishes 

 in black, blue and green colors were changed to brown and red 

 when kept in an aquarium exposed to light,'- that the red color 

 is due to the influence of the light. Specimens of different 

 colors taken from different localities and kept in a zinc tub 

 showed, after several months, in some cases a change of color 

 to that of their surroundings. In April and May the coloration 

 of the young crayfish was studied and the conclusion reached 

 that the red color, due to large, scattered chromatophores of the 

 young crayfish, changed to blue or black or underwent no 

 change, according as the adults were blue, black, or red. 



C. diogenes, he says, furnishes an excellent example of color 

 change. The individuals of this species which, according to 

 him, may be found in any of the smaller streams, in the early 

 spring show various colors, but later in the year are nearly all 

 red. They burrow during the winter, and come out in the 

 spring much the color of the soil, and these colors are gradu- 

 ally turned to red in the open sunlight. 



He concludes, then, that the colors of crayfish are due to two 

 causes, the influence of environment and the effect of sunlight, ^^ 

 and that in all cases these colors serve as protection against ene- 

 mies. 



The question of coloration is by no means a simple one, and 

 without opportunity for an examination of the literature, or 

 more detailed observations than I have been able to make, I do 

 not care to offer explanations, but may call attention to one or 

 two facts which have come to my notice. The colors of a spe- 

 cies are certainly not always the same when found in different 

 localities, but I have never been willing to state that the differ- 

 ence should be regarded as a protective adaptation, although 

 this might be the case. Mr. Kent states that the change in 



12. Of this he says: "This is a difficult experiment to carry out. Crayfish which live in 

 deeper water become strongly photopathic and can endure only very weak light. It was neces- 

 sary at first to place the aquarium with the crayfishes in diffused light and to allow them 

 to become accustomed by degrees to the changed conditions." It is unfortunate that he does 

 not give la more detail the injurious effect of the light upon the animals. In nature some of 

 the burrowing forms are exposed to light of considerable intensity upon emerging from their 

 burrows in the spring. So far as has been recorded, the cave forms are not affected by exposure 

 to light. Compare Putnam's observations on C. pelLucidus. 



Vi. He mentions in the first part of the paper the effect of sunlight in changing the color of 

 pigment when removed from the animal, but, with the exception of heat, does not consider 

 other factors which might produce this change. 



