64 John Henry Comstock 



tirely wanting. Sometimes, as in Danais, remnants of the 

 basal part of the branches of media project back into the dis- 

 cal cell from the discal vein (Fig. 13) ; while in many other 

 butterflies the branches of media are so completely united with 

 radius and cubitus that there is no indication of the fact that 

 they do not belong to these systems of veins (Fig. 14). 



It is probable that in none of the Palceodictyoptera were the 

 wings plaited, as they are in many existing insects ; although 



Fig. 13. — Fore wing of Danais. 



in some, they were broadly folded. And if we except the 

 anal furrow (vein VIII), already referred to, all of the veins 

 were of the type that is termed convex ; that is, they were 

 more prominent on the upper surface of the wing than on the 

 lower. 



We thus see that the evidence of the Palseodictyoptera does 

 not corroborate the theory of Adolph and Redtenbacher as to 

 the primitive type of the wings of insects. Instead of the 

 primitive wing consisting of regularly alternating concave and 

 convex veins, as described by them, it is probable that the 

 concave veins are a later development, either arising de novo ox 

 being modified convex veins, excepting always the anal fur- 

 row (vein VIII), regarding the origin of which we know 

 nothing. 



Concave veins have evidentlj^ arisen to meet two distinct 

 needs : first, in those insects in which the wings have become 



