EVOLUTION BY LOSS 



wild mouse obtain also pale gray, pale black, 

 pale cinnamon, and pale brown varieties, all 

 within two generations from the cross. 



Now the pale modification is distinct from 

 the pink-eyed modification, and independent of 

 it in transmission. Accordingly, it is possible 

 to have the two modifications combined in the 

 same race. Thus arises a series of pale pink- 

 eyed grays, blacks, cinnamons, browns, and 

 yellows. Since paleness is in crosses recessive 

 to intense pigmentation, and pink eyes are re- 

 cessive to dark ones, it follows that a variety 

 which is both pale and pink-eyed will breed 

 true to those characteristics without fixation. 



The lightest colored of the pale pink-eyed 

 varieties develop very little pigment indeed, 

 yet the modifications to which they are due 

 are wholly different in nature from the albino 

 variation, as a very simple experiment will 

 show. Cross together an albino of variety (1), 

 page 74, — which is a snow-white animal with 

 pink eyes, — and a pale pink-eyed, brown ani- 

 mal, whose coat is pale straw color, and whose 

 eyes, like those of the albino, are pink. Although 

 both parents are pink-eyed, and one develops no 



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