io8 Experimental Zoology 



The albinos subsequently bred true ; the pigmented types were 

 of two kinds, pure and hybrid. 



Gray versus Black. When the yellow-gray Belgians were 

 mated to the white Angoras, wild gray hybrids were produced. 

 These, as stated above, when inbred, gave both colored and white 

 offspring in Mendelian proportion, but some of the colored in- 

 dividuals were black instead of gray. There were 85 grays to 

 25 blacks. The grays, as stated, were like the wild gray instead 

 of the yellow gray of one grandparent, although a few appeared 

 to contain somewhat more yellow than the wild type. The blacks 

 had no gray, but it is interesting to note that after the first molt 

 a few white hairs appeared, which increased in number with each 

 molt until some of the individuals resembled the silver-gray 

 breeds (chinchilla). The blacks when inbred produced only 

 blacks, the grays were of two kinds, pure and hybrid. 



"The sudden appearance of the black character in the sec- 

 ond generation was quite unexpected as there had been no black 

 individuals in the ancestry of either of the original parents . . . 

 for at least eight generations, and probably many more. The fact 

 that these black individuals appeared in about the proportion 

 of one quarter, and bred true at once, was very significant from 

 the Mendelian point of view. It suggested that the hybrid grays 

 of the first generation were giving off gametes, one half of which 

 contained the factor for black coat color. That it was not intro- 

 duced by both is clear from the absence of black in the first gen- 

 eration." It could not have been introduced with the Belgians 

 because these mated to black gave only grays. The black 

 must, therefore, have been introduced with the albinos. Hurst 

 carried out some further experiments that seemed to substantiate 

 this view. One male, albino Angora mated with four black does 

 produced 16 black young; but another albino female mated 

 with black produced 5 black and 6 gray young. Hurst inter- 

 prets these results to mean that the first albino gave off gametes 

 that all carried black, while the second albino gave off gametes 

 some of which carried black, others gray. When the white male 

 and the white female used in these experiments were mated, only 



