ALLEN. — THE HEREDITY OF COAT COLOR IN MICE. 141 



ch. 4- ch. = gametes of pure chocolate, 



ch. + wh. ^ '' heterozygous chocolate, 



2 ch. + 2 ch. (wh.) = offspring. 



Consequently, one-half the chocolate young from this sort of a cross 

 result from the union of a gamete of the chocolate pigment character 

 with one of the albino character. The latter, however, carries poten- 

 tially the chocolate character, so that the result of the union is to pro- 

 duce a chocolate animal, since no other color element is introduced. It 

 follows that if two chocolate mice of this sort are interbred, the 2-'> per 

 cent of albinos resulting will in like manner possess the chocolate 

 character. 



The unions of gametes are (formula 2): 



ch. -|- wh. 



ch. + wh. 



ch. + 2 ch. (wh.) + wh. 



This the writer has been able to demonstrate by actual experiment. 

 Such albinos from two heterozygous chocolate parents, when bred to 

 chocolate mice, gave chocolate young only. The obvious inference 

 from results of this sort is that the albino gametes formed by a pigmented 

 animal which has the albino character recessive, possess the same pigment 

 'potentiality as the pigment bearing gametes formed by the same animal. 

 An albino, therefore, both of whose parents had the chocolate character 

 only, will produce young of that charactei*, when mated with a chocolate 

 animal. This fact is doubtless the explanation of Bateson's (: OS**) 

 statement that " Miss Durham has found chocolate a simple dominant 

 over albino," for her albino was presumably of chocolate parentage. 



A different result is obtained by mating chocolate mice with albinos 

 of mixed ancestry. The writer made several matings between chocolate 

 mice and albinos, the latter being extracted recessives from crosses be- 

 tween gray house mice and the original stock of albinos previously men- 

 tioned. Four different albinos were paired with as many chocolate 

 mice, and of the 22 resulting young, 20 were gray and 2 black. The 

 black was presumably transmitted through the albino stock, which, as has 

 been shown, seemed to produce a certain number of gametes having the 

 black tharacter. The predominance of the gray character is strong. 

 Bateson (lOS*") records a cross of similar result, wherein a chocolate 

 and an alI)ino gave gray young. 



An interesting and different result was had bv breeding to a chocolate- 



