ox HEEEDIIY I>- BABBITS. 305 



SlTiEMAET OF COAI-COLOUE EeSULIS. 



Ill tte first generation (F^) yellow-grey x white gave all wild 

 greys. In the second generation (FJ, with one exception, the 

 Tj greys proved to be hybrids containing recessive black, for. 

 when bred together, they gave a mixture of grevs and blacks 

 in MendeHan proportions. In the third generation (Fg) the F^ 

 blacks have so far bred true when mated together ; they are 

 recessive to pure grey and give a mixture of greys and blacks 

 when mated with hybrid greys. The F, greys so far appear to be 

 of two kinds, pure and hybrid, and the hybrids bred together 

 give a mixture of greys and blacks in ^Xendelian proportions. 

 From the Mendeliau point of view the above results are what 

 might have been expected had the original parents been grey X 

 black instead of yellow-grey x white. 



Two points therefore appear to demand consideration: — 

 The appearance of the black character, and the disappearance of 

 the vellow-grey character. 



TJie Appearance of the JBlacTc Character. 



The sudden appearance of the black character in the second 

 generation was quite unexpected, as there had been no black 

 individuals in the ancestry of either of the original parents — 

 Eelgian or Angora — for at least 8 generations and probablv 

 many more. The fact^Lat 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 greys of the first generation were giving off 

 cametes, one half of which contained the factor for blaci coat- 

 colour. As these hybrid greys were bred from the yellow-grev 

 Beloians crossed -nith the white A ngora, it appeared that the 

 black factor roust have been introduced hy one or the other of 

 these parents, or by both. 



That it was not introduced by both is clear from the absence 

 of blacks in the first generation. That it was not introduced bv 

 the Belgian is equally clear from the fact that no blacks appeared 

 when the Belgian was mated with a pure black, nor when the 

 Belgians were mated together. From the ]y]endelian point of 

 view, therefore, it would appear that the black factor must have 

 been introduced by the white Angora. This may appear in- 

 credible, and yet, as the following experiments show, it seems 

 to be the only interpretation of the facts. 



LEO', jorsy. — zooLO&T, yoL. ixix. 21 



