INTRODUCTION 



Fig. i. Chromatophores of the squid Loligo: a, contracted; 

 l>, expanded. Bozler, Zeit. vergl. Physiol., 1928, 7, 381, fig. 1. 



visible. In the crustaceans, especially the shrimps, the 

 chromatophores (Fig. 2) are usually groups of cells which 

 may carry each cell for itself a distinctive color. By 

 internal migration these colors 

 become variously dispersed or 

 concentrated, thus adding or 

 subtracting their share in the 

 general color tone of the whole 

 animal. Finally in the verte- 

 brates the great majority of 

 chromatophores (Fig. 3) are single 

 cells of which there are several 

 classes: melanophores, containing 

 dark pigment granules; xantho- 

 phores and erythrophores carry- 

 ing yellow, orange, or red caro- 

 tenoid pigments; and finally, 



Fig. 

 phore 



2. Chromato- 

 with fully dis- 

 persed pigment from the 

 shrimp Palaemonetes . 

 Perkins, Jour. Exp. 

 Zoo!., 1928,50, 101, pi. 1 . 





Inc. 3. Group of chromatophores each with fully dispersed 

 pigment from the tail of the killifish. 



