480 Studies in the Theory of Descent. 



power could work in the same organism in two 

 entirely different directions that it should in the 

 same species lead to the constitution of quite 

 different systems for the larvae and for the imagines, 

 or that it should lead only to the formation of 

 families in the larvae and to sub-orders in the 

 imagines ? If an internal force existed which had 

 a tendency to call into existence certain groups of 

 animal forms of such a nature that these constituted 

 one harmonious whole of which the components 

 bore to one another fixed morphological relation- 

 ships, it would certainly have been an easy matter 

 for such a power to have given to the larvae of 

 butterflies some small character which would have 

 distinguished them as such, and which would in 

 some measure have impressed them with the stamp 

 of " Rhopalocera? Of such a character we find 

 no trace however ; on the contrary, everything goes 

 to show that the transformations of the organic 

 world result entirely from external influences. 



