HEREDITY 



other than the albino; in the wide series, of 

 animals so extensively pigmented that they 

 would readily pass for the ' ' Irish type, ' ' which 

 has white on the belly only, but which is known 

 to be in crosses a Mendelian alternative to the 

 hooded type. By selection we have practically 

 obliterated the gap which originally separated 

 these types, though selected animals still give 

 regression toward the respective types from 

 which they came. But this regression grows 

 less with each successive selection and ulti- 

 mately should vanish, if the story told by these 

 statistics is to be trusted. As yet there is no 

 indication that a limit to the effects of selec- 

 tion has been reached. 



From the evidence in hand we conclude that 

 Darwin was right in assigning great importance 

 to selection in evolution; that progress results 

 not merely from sorting out particular com- 

 binations of large and striking unit-characters, 

 but also from the selection of slight differences 

 in the potentiality of gametes representing the 

 same unit-character combinations. It is pos- 

 sible to ascribe such differences to little units 

 additional to the recognized larger ones, but 



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