MELANOPHORES OF THE HORNED TOAD 277 



and temperature. The great mass of data upon the chromato- 

 phores of other lizards has been reviewed recently by von Ryn- 

 berck ('06) and by Fuchs ('14). 



Horned toads have been obtained from collectors in various 

 parts of Texas and Oklahoma. They may be had in large num- 

 bers between April and September. In the laboratory they were 

 kept in a large sunlit cage, where they thrived on a diet of meal 

 worms. In summer the animals were kept in cages out of 

 doors and fed on various insects in season. Horned toads do 

 not feed if kept in the laboratory through the winter. They 

 become greatl}^ emaciated and usually die before spring If 

 these lizards are placed in a dark, cool cellar, they go into hiberna- 

 tion and remain in very good condition all winter. 



Experiments have been carried on in the Zoological laboratory 

 of Harvard College at Cambridge, Massachusetts, in the physi- 

 ological laboratory of the Harvard Medical School in Boston, 

 and in the laboratory of the United States Bureau of Fisheries 

 at Woods Hole. I wish to acknowledge my indebtedness to Dr. 

 G. H. Parker for his kindness in directing this investigation and to 

 Dr. Walter B. Cannon for valuable advice on certain phases of 

 the work. 



II. THE MELANOPHORE REACTIONS OF THE HORNED TOAD 



1. Descri-ption of color changes 



Under certain conditions the ground color of the upper surface 

 of the horned toad is fuscous.- Across the back run three irregu- 

 lar bands of fuscous-black, bordered posteriorly with a bright 

 amber-yellow line, which stands out prominently in contrast to 

 the dark ground-color. Similar fuscous-black bands, not bor- 

 dered with yellow, extend across the legs. The flattened scales 

 which extend in a row along the sides of the body are black at 

 the base, white at the tip. Under other conditions, the ground- 

 color becomes drab, drab-gray, or cinnamon-buff, frequently 

 flecked with black. The amber-yellow lines across the back no 



- The color nomenclature of Ridgway ('12) is used throughout this description. 



