CHAPTER VIII 



EXPERIMENTS WITH OTHER MAMMALS AND WITH BIRDS 

 Experiments with Guinea Pigs 



THE hair of wild guinea pigs or ca vies shows the same three 

 pigments present in mice, viz. black, chocolate, and yellow. 

 Domesticated cavies may show the following colors : the agouti 

 cavy with the hair containing the black, yellow, and chocolate 

 pigment. The yellow cavy with only yellow pigment. The 

 red cavy is a dark, yellowish red. The chocolate cavy has 

 chocolate pigment predominating. The black cavy has black 

 pigment predominating over the other two. The albino cavy 

 is principally white, although an entirely white individual seems 

 never to occur ; for pigment is generally found in the extremities 

 of the body, on the feet, or nose, or ears, and sometimes in hairs 

 on the body also. 



In addition to these there occur spotted or pied races. Any 

 one of the colors may be combined with white. A great variety 

 of markings result in this way, since the pigment areas may be 

 of different colors. 



Brindled cavies have black and red hairs interposed in the 

 same patches. Roan animals have white hairs interspersed 

 with red ones. Silvered cavies have black and white hairs. 



Castle has carried out through several years experiments 

 with differently colored and marked races of these animals. 



Crossing Uniformly Colored Types. The self-colored races, 

 as well as the albinos, breed true : thus Castle found albinos bre.d 

 inter se gave 156 young, all albinos; pure pigmented individ- 

 uals gave 261 young, all pigmented. On the other hand, al- 

 binos mated to pigmented animals gave in the first generation 



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