Evolution and Taxonomy 



75 



and in such cases have not been considered, heretofore, as 

 parts of the discal vein. The intermediate portions of the 

 discal vein maj' be merelj- the branches of media somewhat 

 bent out of their primitive course. This condition is ilkis- 



FiG. i8. — Eacles. The hind wing is enlarged more than the fore wing. 



trated by the hind wings of Packardia (Fig. i6). Here the 

 first branch of media has been drawn towards radius as a re- 

 sult of the change in tlie source of its air supply ; and in a 

 similar way the third branch of media, receiving a large part 

 of its air from cubitus, is bent towards cubitus. In other 



