1930] Wing Venation of the Odonata and Agnatha 261 
plaiting. Such was the situation acquired, e. g., in Camplyop- 
tera eatoni Brongn., a species referred by Handlirsch to 
the Megasecoptera. In the drawing by Handlirsch the char- 
acter of the intercalary sectors is very clear. Furthermore, 
according to Handlirsch’s drawing the change of some longi- 
tudinal veins into intercalary sectors had begun in Lycocer- 
cus and in Epithethe. In other Palseodictyoptera we do not 
notice this. In groups rich with longitudinal veins as the 
Spilapteridse, Lamproptilidae, Polycreagridse, the plaiting 
was already suggested, but it never came to a formation of 
inserted sectors. The plaiting, together with the forming of 
inserted branches, is a very important mechanical improve- 
ment, which allowed lightening of the wing a great deal 
without loss of its firmness and elasticity. 
Leaving aside for awhile the question of the origin of 
the peculiarities of tracheation in may-flies, which we will 
consider together with the tracheation of dragon-flies, let 
us turn to the venation of dragon-flies. The peculiarities of 
dragon-flies enumerated at the very beginning of this 
article, are, as stated, rather the peculiarities of interpreta- 
tion, which result from the nature and insufficiency of the 
method employed (“method of ontogeny”), and not at all 
from the actual venation. Putting aside these hypothetical 
considerations, let us compare the wings of dragon-flies 
with those of may-flies and Palseodictyoptera. 
First of all one should note that in form as well as in the 
general distribution of the main longitudinal veins and in 
the smaller reduction of the anal area, the Anisoptera show 
a great deal more primitive features than the Zygoptera, 
whose wings were subject to very great changes; one could 
say that in the Anisozygoptera everything in general is 
much closer to the Zygoptera, and as a matter of fact 
merges into them in their more primitive Liassic represent- 
atives (Archithemidse, Heterophlebiidse) ; they still partly 
resemble the Anisoptera in their form, configuration of the 
anal area, and in general distribution of the main veins. 
In this collective Liassic complex the triangle (e. g., in 
Heterophlebiidse) begins to take form, but further develop- 
ment was reserved only for such groups in which the tri- 
angle succeeded in acquiring its typical aspect, — and these 
were the groups that formed the Anisoptera ; others, where 
