On the Seasonal Dimorphism of Butterflies. 105 



the physical constitution of the species that this 

 manifests itself by other colours and markings. 

 Now when this newly acquired physical constitu- 

 tion, established, as we may admit, throughout 

 a long series of generations, is again submitted 

 to a constant change of climate, this influence, 

 even if precisely similar to that which obtained 

 during the period of the first form of the species, 

 cannot possibly reproduce this first form. The 

 nature of the external conditions may be the 

 same, but not so the physical constitution of the 

 species. Just in the same manner as a Pieris (as 

 has been already shown), a Lyccena, or a Satyrus, 

 produces quite different varieties under the trans- 

 forming influence of the same climate, so must the 

 variation originatingfrom the transformed species of 

 our present case after the beginning of the primary 

 climate be different from that primary form of the 

 species, although perhaps in a less degree. In 

 other words, if only two different climates alter- 

 nated with each other during the earth's geological 

 periods, every species of butterfly submitted to 

 these changes of climate would give rise to an 

 endless series of different specific forms. The 

 difference of climate would in reality be greater 

 than supposed, and for any given species the 

 climatic variation would not only occur through 

 the periodic shifting of the ecliptic, but also through 

 geological changes and the migrations of the 

 species itself, so that a continuous change of 



