34 Studies in the Theory of Descent. 



three generations placed upon ice should give, 

 for the greater part, the form Telamonides, for the 

 lesser portion Walshii, and for only a few, or per- 

 haps no individuals, the form Marcellus, This 

 prediction is based on the view that the tendency 

 to revert is on the whole great ; that even with the 

 first summer generation, which was the longest 

 exposed to the summer climate, a portion of the 

 pupae, without artificial means, always emerged as 

 Telamonides, and another portion as Marcellus. 

 The latter will perhaps now become Walshii by 

 the application of cold. 



One would expect that the second and third 

 generations would revert more easily, and in a 

 larger percentage, than the first, because this latter 

 first acquired the new Marcellus form ; but the 

 present experiments furnish no safe conclusion on 

 this point. Thus, of the first summer generation 

 only seven out of sixty-seven pupae hibernated, 

 and these gave Telamonides ; while of the second 

 generation forty out of seventy-six, and of the 

 third generation twenty-nine out of forty-two 

 pupae hibernated. But to establish safer conclu- 

 sions, a still larger number of experiments is 

 necessary. According to the experience thus far 

 gained, one might perhaps still be inclined to 

 imagine that, with seasonal dimorphism, external 

 influences operating on the individual might 

 directly compel it to assume one or the other 

 form. I long held this view myself, but it is, 



