COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 47 



(see p. 9). The black-footed guinea-pig has the former, which it 

 transmits to its offspring ; it does not possess the latter and its offspring 

 never do, unless a mating has been made with an animal having pig- 

 mentation of that sort. The black-footed red guinea-pig, as regards 

 black pigmentation, is in exactly the same condition as an albino with 

 dark-pigmented extremities ; centripetal black pigmentation is fully 

 latent in it. 



Black-eyed white animals, of the sort which I have had, and ani- 

 mals like 9 915, are centripetally pigmented animals in which the 

 capacity to form black pigment in the typical central patches is semi- 

 latent, /. e., they may apparently transmit the character in a fully active 

 condition, when mated inter se, across with animals having a different 

 type of pigmentation being unnecessary for this purpose. 



Darbishire's pink-eyed but centripetally pigmented mice, if they 

 possessed at all the capacity to form eye-pigment, must have possessed 

 it in a more than latent condition, for they bred true inter se, and though 

 a cross with albinos brought the character into full activity, there are 

 strong reasons for believing, as we shall presently see, that the capacity 

 to form eye-pigment was recovered, not from the pink-eyed animal, 

 but from the albino with which it was mated. It is to be expected 

 that continued selection and inbreeding of black-eyed white guinea- 

 pigs would establish a condition of the coat-pigment patches similar 

 to that of the character eye-pigmentation in Darbishire's pink-eyed 

 mice, a condition which goes beyond the latency of centripetal pig- 

 mentation in albinos, and may, for all we at present know, amount to 

 elimination of the character in question from the germ. This question 

 offers an attractive field for further investigation. 



Comparison 'with pink-eyed mice. The dark-eyed mice obtained 

 by Darbishire ( : 04) upon mating pink-eyed spotted mice with albinos, 

 yielded an interesting result when bred inter se. Approximately one- 

 fourth of the young were, as we should expect, albinos ; one-half were 

 dark-eyed, like their parents, the primary hybrids ; and one-fourth 

 were pink-eyed and spotted. We should naturally expect the dark-eyed 

 young (like their parents) to contain recessive albinism, and the pink- 

 eyed spotted ones to be free from it, like their pink-eyed grandparents. 

 While in many cases this was undoubtedly true, in others it was not 

 true ; for Darbishire's breeding experiments show that some of the 

 dark-eyed animals did not contain recessive albinism, and that some of 

 the pink-eyed ones did. Further, the "extracted" albino young in 

 some cases behaved differently from their albino grandparents in 

 crosses with pink-eyed spotted animals. They produced pink-eyed 

 as well as dark-eyed hybrids, the two sorts being approximately equal 

 in number (7 pink-eyed to 6 dark-eyed, Darbishire, : 04, Table D, p. 24). 



