HEREDITY 



pigmented cells outside the brain, through 

 stages in which cells were present without pig- 

 ment, and others in which pigment was visible 

 within the brain but no cells outside it were 

 developed, and finally to those in which all 

 traces of the eye had vanished, cells and pig- 

 ment alike. By selection in three successive 

 generations of the mother having the rudi- 

 mentary eye best developed offspring were 

 obtained, 90 % of which had the pigmented 

 eye, and which would therefore pass for ani- 

 mals of a wholly different genus. The degree 

 of development of the organ in the last genera- 

 tion was also greater than in the previous 

 generations. Here within a pure line produced 

 by parthenogenesis selection served to augment 

 both the degree of development of an organ 

 and the frequency of its occurrence within the 

 race, a result precisely parallel to that which 

 I obtained some years ago by selection in the 

 case of a rudimentary fourth toe in the guinea- 

 pig. The experiment with Daphnia is not open 

 to the objection that may be offered to the 

 guinea-pig experiment, that it is possibly a 

 result of gametic segregation and recombina- 



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