356 LIGHT AND THE BEHAVIOR OF ORGANISMS 



It is well known that many of the spider crabs fasten 

 seaweeds and other objects to the carapace. Minkiewicz 

 placed the crabs into aquaria with the sides and bottom 

 uniformly colored and added bits of colored paper, some 

 corresponding to the walls of the aquarium and others not. 

 He claims that the animals selected those pieces which 

 harmonized with their environment in color, and fastened 

 them to the surface of the body and legs so that they became 

 inconspicuous. " Les resultats sont ... vraiment f rap- 

 pants, la couleur du costume correspondant toujours 

 precisement a celle du milieu " (1907, p. 41). In a black 

 aquarium however there was no evidence of selection, and 

 it appears that the animals were unable to distinguish 

 between green and yellow. 



The author also says that if the crabs are left on a 

 given color for some time and then transferred to an 

 aquarium which is variegated in color, they come to rest 

 in that part which corresponds in color with that from 

 which they were taken. 



In the experiments on the hermit crabs Minkiewicz 

 illuminated the two halves of an aquarium with light 

 of different colors, placed the animals so that the two 

 eyes were exposed to light of different colors, and found 

 that the creatures turned toward the color indicated by the 

 arrows below; i.e., in case of black and red in the aquarium 

 they went toward the red, in case of red and yellow, toward 

 the yellow, etc., as indicated: 



black -^ red — > yellow -^ blue -^ violet-^ green — > white. 



If the crabs are kept in a jar and exposed to their own 

 excreta for some time their reactions to colors gradually 

 change as follows: 



Normal : red — > blue ^^ green. 

 red -^ green — ^ blue, 

 green -^ red — > blue, 

 green -^ blue — > red. 



