606 PROCEEDINGS OP THE AMERICAN ACADEMY. 



spring, and in subsequent generations both gray individuals and white 

 individuals occur approximately in the proportions demanded by Mendel's 

 principles of dominance and segregation. No better illustration of Men- 

 del's law has yet been produced than is afforded by the cross between 

 gray and white mice. 



(b) In Other Mammals, in Fishes, and in Plants. 



In the case of guinea-pigs, we have many times mated together albinos 

 born of mottled parents, or obtained by mating a mottled with a white 

 animal, but never with any but the expected Mendelian result, all the 

 young being albinos. 



In the case of rabbits, the same law appears to hold. Professor R. T. 

 Jackson kindly placed at our disposal last summer three white rabbits, a 

 male and two females, all born in the same litter, of spotted parentage. 

 The two females have borne by their brother, in three litters, seventeen 

 young, all albinos. 



In man, Farrabee (: 03) and Castle (: 03) have recently shown albi- 

 nism to be in all probability recessive. 



As to fishes, Dr. Hugh M. Smith, of the United States Fish Commis- 

 sion, informs us that in one of the State fish-hatcheries of this country 

 there is bred as a curiosity a race of albino trout which " breed true," 

 indicating that the albino character is recessive. 



In plants, more than two-thirds of the Mendelian cases mentioned by 

 de Vries (:02, p. 146) are cases of "depigmentation" of flowers or fruit, 

 the depigmented condition being invariably recessive in crosses with the 

 normal condition. 



It appears, then, that in organisms in general, albinism behaves as a 

 recessive character in heredity.* 



III. Partial Albinism a Mosaic of Dominant and Recessive 

 Characters, and a Unit in Heredity. 



Darbishire (:02 ) finds that in crosses between a peculiar race of par- 

 tial albino mice and true albinos, the albinism does not entirely disappear 

 in the offspring, and he thinks that this weighs heavily against the entire 



* The only exception known to the writers is the dominance of white plumage, 

 in certain crosses of poultry, as recorded by Bateson and Saunders (: 02). Yet the 

 dominant character in this case is one of partial albinism only, and its dominance 

 is not invariable. We suspect that the dominance of white plumage results from 

 its coupling in the gametes with some other character strongly dominant by nature. 



