I02 Experimental Zoology 



cattle have been able to do it seems not improbable that this 

 might be accompHshed. 



Castle draws attention to the curious point that red and yel- 

 low cavies, having no black pigment in their coats, do not trans- 

 mit black coat-pigment to their offspring, although they do 

 transmit black eye-pigment. It would be erroneous, he thinks, 

 to conclude from this that the eye-pigment is something alto- 

 gether different in its inheritance from coat color, because when 

 mice with coat patches but devoid of eye-pigment are mated 

 with albinos, the offspring have pigmented eyes — a character 

 that neither parent possessed 



Heredity oj the Rough Coat. — Some races of domesticated 

 guinea pigs show the hair arranged in whirls or rosettes. When 

 best developed the rosettes are found around the following 

 paired centers: (i) the eye, (2) a point immediately behind the 

 ear, (3) the shoulder, (4) a point dorso-lateral on the body, 

 (5) the hip, (6) the groin, (7) each of the single pair of mammas ; 

 and from two unpaired centers, viz. (8) the middle of the fore- 

 head, and (9) the navel. The direction of the hair is also re- 

 versed on the toes. 



These rough-coated individuals breed true. When crossed 

 with smooth-haired individuals the rough character dominates. 

 The rough character of the offspring is usually as fully developed 

 as in the rough parent. However, certain smooth individuals 

 when crossed bring about a weakened condition of the rough 

 character, some of the rosettes being less developed or even 

 absent. These partially rough individuals may transmit to 

 their descendants the fully rough condition. The result is 

 important in that it shows that what we must regard as a new 

 character in the species, viz. a rough coat, dominates when a 

 back cross is made.^ On the other hand. Castle has also found 

 that repeated crossing of rough individuals with prepotent smooth 

 ones results in further weakening of the rough character until it 

 is almost eliminated — one after another of the rosettes disap- 

 pearing. The weakening does not follow a definite dechne, but 



^ See Castle's analysis, pp. 47-50. 



