ioo Studies in the 7^/ieory of Descent. 



VI. 



GENERAL CONCLUSIONS. 



I SHALL not here give a repetition and summary 

 of the results arrived at with respect to seasonal 

 dimorphism, but rather the general conclusions 

 derived from these results ; and, at the same time, 

 I may take the opportunity of raising certain 

 questions which have not hitherto found expres- 

 sion, or have been but briefly and casually stated. 

 It must, in the first place, be admitted that 

 differences of specific value can originate through 

 the direct action of external conditions of life only. 

 Of the truth of this proposition there can be no 

 doubt, after what has been above stated concern- 

 ing the difference between the two forms of any 

 seasonally dimorphic species. The best proof is 

 furnished by the older systematists, to whom the 

 genetic relationship of the two forms was un- 

 known, and who, with unprejudiced taxonomy, in 

 many cases indicated their distinctness by separate 

 specific names. This was the case with Araschnia 

 Levana and Prorsa, Euchloe Bella and Auso- 

 nia, E. Belemia and Glance, Plebeius Polysperchon 

 and Amyntas. In the presence of these facts it 



