120 THE AMERICAN NATURALIST. [Vou. XXXIII. 
represented by Fig. 69. In the hind wing, vein C2 is appar- 
ently a branch of the first anal vein (marked A in the figure) ; 
but in the fore wing, which is less modified, its primitive con- 
nection is preserved; although even here a prominent bend 
has brought it near to the anal vein, and only a step more 
would be required, the fading out of the basal section, to reach 
Fie. 69. — Wings of Ephemera. 
the condition attained in the hind wing. But the concave 
nature of this vein in the hind wing indicates its homology in 
spite of its misleading basal connection. 
It should be remembered that the convex or concave nature 
of a vein is the result of a corrugation of the wing and not the 
cause of this corrugation. The theory of Adolph that the two 
sets of veins have a different ontogenetic development has abso- 
lutely no foundation in fact, as will be seen when we come to 
study the development of wing-veins, and as was suspected by 
Brauer and Redtenbacher.! 
The primitive insect wing was doubtless flat. It makes no 
1 Zoologischer Anzeiger, 1888, p. 443- 
