10 COLOR CHANGES IN ANIMALS 



lished a number of years after Hogben's earlier work, 

 and though they add somewhat to the complexity of the 

 picture of chromatophoral control in amphibians, they 

 leave that picture essentially as it was originally out- 

 lined by Hogben himself: nerves relegated to the back- 

 ground, perhaps entirely excluded, and hormones the 

 all-important factors. The contrast between this new 

 way of conceiving the adjustment of amphibian chro- 

 matophores to environmental changes and that envis- 

 aged by the older workers is enormous. As was pointed 

 out by Hogben in 1924, this view of color-cell activation 

 sets off the amphibians in strong contrast with the fishes 

 and the lizards, in both of which there appeared to be 

 ample and complete evidence for the nervous control of 

 their color-cells. 



Quite independent of the work on amphibians, but 

 emerging eventually in much the same way, is that done 

 by recent investigators on crustaceans. Like the frogs 

 and toads, shrimps and other crustaceans had never 

 yielded in nerve-cutting experiments evidence favorable 

 for a nervous interpretation of the control of their chro- 

 matophores. In 1925 Koller noticed that when the 

 blood of a dark-tinted Crangon, a common Atlantic 

 shrimp, was drawn and injected into a pale one the 

 latter quickly grew dark. This at once suggested that 

 in these animals neurohumors may be in the blood and 

 may be the means of controlling the color-cells. This 

 idea was followed up by Perkins who in 1928 published 

 an account of the color changes in another /Atlantic 

 shrimp, Palaemonetes. Perkins was unable to repeat 

 with success in this form the experiment on the trans- 

 ference of blood carried out by Koller on Crangon, but 

 he nevertheless sought in the body of Palaemonetes for 

 an organ that might produce a humor controlling the 

 color-cells. This he finally found in the eye-stalks of 



