54 GENETIC STUDIES OF RABBITS AND RATS. 



In 1912 1 I described a peculiar guinea-pig, which, in the light of 

 the present case, I am inclined to explain in the same way as the 

 tri-color rat, as a non-transmissible though not of necessity a purely 

 somatic mutation. At that time I characterized the guinea-pig in 

 question as a "pink-eyed individual with a colored coat," but this 

 is not a very good description for it. The description fits better a 

 genuine genetically transmissible variety that was then unknown to 

 us, but which curiously enough was soon to appear in our breeding- 

 pens from stock that had recently been obtained in Peru. The indi- 

 vidual, whose peculiarities were not transmitted to its offspring, 

 was by pedigree a heterozygote between albinism and pale black. 

 Such a heterozygote I believe it in fact to have been, but in appearance 

 it was white, except for some small spots of pale black ("blue") on 

 the right side of the head and on the hips. The head pigmentation 

 extended as a "faint pigmented streak" on to "the iris of each 

 eye." The mother of this animal was blue, the father cream (which 

 is recessive to blue), but he also transmitted albinism. He can not 

 have transmitted blue, since that is dominant to cream. Undoubt- 

 edly, then, the egg from which this individual developed transmitted 

 color (C) and blue (E) which lie in different chromosomes. But 

 the father transmitted albinism (c) and cream (e), which are reces- 

 sive allelomorphs of C and E respectively. Evidently it was the 

 maternal chromosome bearing C which was lost from the greater 

 part of the ectoderm of the embryo, since no other loss would have 

 produced an uncolored coat and eye. Whether or not E was lost 

 in the same regions can not be determined, but since all colored 

 areas were blue, not cream, it is evident that wherever C was re- 

 tained, E was retained also. 



The peculiar individual was a female and produced three young, 

 all albinos as I recall, by an albino sire, before her untimely death. 

 It can not be stated, therefore, whether the germ-cells were hetero- 

 zygous in nature or were like the greater part of the coat, pure albino, 

 inherited from the sire alone. Certainly none of the three develop- 

 ing ova transmitted the mosaic condition found in the mother. It 

 seems probable, though it is regrettably unverifiable, that no young 

 mottled like the mother would have been obtained, had we been 

 able to obtain a much larger number of young. 



1 Science. 36, p. 508. 



