ALLEN. — THE HEREDITY OP COAT COLOR IN MICE. 115 



in the case of mice, as the patches about the head are uot easy of 

 eliminatiou. 



To carry the reduction of pigmentation still farther would be to bring 

 about a reduction of tlie pigment in the eyes of a black-eyed white ani- 

 mal. Batesou (:03") mentions a strain of black-eyed white mice whose 

 eyes were a "blackish red," so that apparently it is possible to reduce 

 the eye pigment in a black-eyed white animal. Darbishire's pink-eyed, 

 fawn-white mice show that depigmentation of the eye may take place 

 independently of elimination of the coat patches. If the reduction of 

 the patches by proper selection is possible, we may conceive of a total 

 albino mouse derived from a pigmented stock, and so potentially a mo- 

 saic, which, nevertheless, if bred to an albino might give totally pigmented 

 young. Evidence of this is found in Bateson's (: 03") statement that 

 the black-eyed white mice do not breed true to that condition even inter 

 se, and a cross with an albino of dissimilar ancestry would probably have 

 the effect of upsetting the condition of restricted pigment still further. 

 This indeed is the result which, as I am authorized by Professor Castle 

 lo state, has usually been obtained by him with guinea pigs. For on 

 breeding together an albino and a black-eyed white animal, the young 

 are more or less extensively pigmented, depending somewhat on the 

 parentage of the albinos used. Other evidence showing the comparative 

 instability of this condition of extreme pigment reduction is afforded by 

 the white cattle of Scotland, the so-called "White Forest breed." Ac- 

 cording to E. L. Sturtevant ('74) this breed is characterized by the 

 absence of pigment from the entire surface of the body, save the hoofs, 

 horns, and nose-skin, which are black, and the ears, which are usually 

 red. The ej'es also are pigmented. The herds of this animal formerly 

 kept in certain private parks of tlie British Isles show evidence of long 

 inbreeding, and it is known that a severe process of selection has been 

 practised to keep the breed up to the desired standard. Frequently pig- 

 ment patches occur on the neck or sides of the offspring of two typically 

 marked animals, and such blemishes in the herd are customarily removed 

 at once. 



Evidently a case of this sort among plants is that cited by Naudin 

 ('65), in wliich two varieties of Datura were crossed. The one was an 

 albino race with white flowers (D. laevis), while the other was also white 

 flowered, but showed a slight pigmentation of the stem in the region of 

 the nodes (D.ferox). This union always resulted in a blue flowered 

 plant similar to the usual D. tatula. Evidently the form ferox was a 

 partial albino in which the pigmentation was extremely reduced in the 



