1930 ] Wing Venation of the Odonata and Agnatha 265 
sented in the fossil Heterophlebiidse 10 by a longitudinal and 
usually uneven vein anterior of Cu. All these comparisons 
lead to the conclusion that in the dragon-flies, Cui of the 
authors is not at all Cui, but that it corresponds to Cu 2 of 
the may-flies. Cui of the may-flies does not exist any longer 
in the dragon-flies.* It is very possible that Cui of the may- 
flies is CuAi, but at present we cannot ascertain this. 
The top side of the triangle was formed, according to 
Needham, by a cross-vein between Cu and M, slanting 
distally 11 . This is contrary to certain facts. In Neurothemis 
oculata Fab., for instance, and even more in Aeschnidium, 
the region of the triangle, as well as other areas, is occupied 
by a thick net and between M from one side, and Cu and 
the top side of the triangle from the other side, is distrib- 
uted a thick series of short cross-veins. It is absurd to 
attribute the formation of the upper side by an inclination 
of a cross-vein. The outside as well as the upper side very 
likely was crystalised, as it were, directly from the network 
(certainly of very fundamental origin) under pressure of 
mechanical causes. Furthermore, this vein exists in order 
to join the basal part of Cu with M. If it came into that 
position by the slanting of a cross-vein (between Cu and M) 
one would not understand how it could pass by M and termi- 
nate on the exterior side of the triangle, a short distance 
down from M; this condition one encounters sometimes in 
the Libellulidse and we find it in Heterophlebia, where it 
goes to the exterior side and is almost parallel to M (hind 
wing, H. dislocata). Such diversity points to the diverse 
nature of the formation of this vein. As soon as this wing- 
structure, which was derived from the configuration of the 
venation and of the wing form and for the working of its 
parts, acquired the formation of a triangular frame, its two 
sides (the interior side is formed by the downward projec- 
10 E. g., Heterophlebia dislocata (Handlirsch, 1. cit., pi. 42, fig. 3). 
11 Needham, 1. cit., p. 717, fig. 12. 
* At the request of Dr. Martynov, the following sentences, which 
were in the original, have been omitted: “In the Protodonata (Mega- 
neura, Boltonites, Typidae) we also usually find the simple anterior 
branch CuAi, and the branch CuP joined to the anal group. This 
seems to point to the conclusion that Cu 2 of the dragon-flies is CuP, 
and that CuA disappears in them.” 
