CASTLE AND ALLEN. THE HEREDITY OF ALBINISM. GOO 



sives), the offspring are coinmouly all gray or black in color, none 

 spotted. Here we find that dominant and recessive characters have 

 abandoned the balanced relationship which they had in the spotted 

 parent, and returned to the ordinary relationship of a dominant to a 

 recessive character. 



Just as in mosaic individuals the law of dominance is suspended, so, 

 too, in the formation of their gametes the law of segregation is commonly 

 suspended also. The gametes, as well as the soma, of a mosaic indi- 

 vidual are commonly mosaic, containing side by side the dominant and 

 the recessive characters. For it is evident from the experiments of 

 Haacke, von Guaita, and Darbishire that the spotted mice employed by 

 them in crosses with albino mice did not form any gametes containing 

 only the recessive (albino) character, otherwise albino offspring would 

 have been produced, but not one was produced. Hence segregation of 

 the pigment-forming character from the albino character cannot have 

 occurred at the formation of gametes in these several cases, but the 

 gametes themselves must have possessed a mosaic (or else a dominant) 

 character. 



A similar explanation must be made of certain results obtained by 

 one of us in crossing black-white (not dancing) mice with albino mice. 

 Two spotted males of a black-white stock which bred true inter se, were 

 crossed with albinos. The offspring were like those obtained by Haacke 

 in crossing Japanese dancing mice with albinos, namely, mice uniformly 

 gray or black in color, though sometimes with a fleck of white on the 

 belly, or with oue or more white bands on the tail. Of the forty-three 

 young produced by this cross, twenty-eight were gray, and fifteen black. 

 The fact that no albino offspring were produced shows that the spotted 

 males formed no recessive gametes, but only those which were either 

 mosaic, or else purely dominant, in character. But if dominant gametes 

 had been formed by segregation from a dominant-recessive mosaic, 

 we should expect that by a residual process recessive gametes would be 

 formed also. The latter not having been formed, it is safe to suppose 

 that the former were not formed either, but that all the gametes formed 

 by these spotted males were mosaic. 



That the albino character entered as a latent constituent into the gray 

 or black hybrids formed by the cross just described, is shown conclusively 

 by the character of their offspring. When bred inter se they produced 

 albino as well as pigmented offspring, and approximately in the ratio, 

 1:3; or, when bred to albinos, in the ratio, 1:1. 



Accordingly, in the original cross described, we have a case of simple 

 vol. xxxviii. — 39 



