PRESIDENT’S ADDRESS 337 
and attempts at flight they would grow larger, until they would be- 
come permanent organs, though still rudimentarv, as in many exist- 
ing Orthoptera, such as certain Blattariae and Pezotettix. By this 
time a fold or hinge having been established, small chitinous pieces 
enclosed in membrane would appear, until we should have a hinge 
flexible enough to allow the wing to be folded on the back, and 
also to have a flapping motion. A stray tracheal twig would 
naturally press or grow into the base of the new structure. After 
the trachea running towards the base of the wing had begun to 
send off branches into the rudimentary structure, the number and 
direction of the future veins would become determined on simple 
mechanical principles. The rudimentary structures beating the air 
would need to be strengthened on the front or costal edge. Here, 
then, would be developed the larger number of main veins, two or 
three close together, and parallel. These would be the costal, sub- 
costal and median veins. They would throw out branches to 
strengthen the costal edge, while the branches sent out to the outer 
and hinder edges of the wings might be less numerous and farther 
apart. The net-veined w ings of Orthoptera and Pseudoneuroptera, 
as compared with the wings of Hymenoptera, show that the wings 
of net-veined insects were largely used for respiration as well as 
for flight, while in beetles and bees the leading function is flight, 
that of re espiration being quite subordinate. The blood would then 
supply the parts, and thus respiration or aeration of the blood 
would be demanded. As soon as such expansions would be of even 
shght use to the insect as breathing organs, the question as to their 
permanency would be settled. Organs so useful both for flight 
and for aeration of the blood would be still further develop: ‘d, until 
cuey would become permanent structures, genuine wings. Thev 
would thus be readily transmitted, and being of more use in adult 
life during the season of reproduction, they “would be still further 
developed, and thus those insects which could fly best. i. e., which 
had the strongest wings, would be most successful in the struggle 
for existence. Thus also, not being so much needed in laryal life 
before the reproductive organs are developed, they would not be 
transmitted except in a very rudimentary way, as perhaps a mass 
of internal indifferent cells (imaginal discs), to the larva, being 
rather destined to develop. late in larval and in pupal life. Thus 
the development of the wings and of the generative organs would 
go hand in hand, and become organs of adult life.” 
That there are insuperable objections to this view will be 
evident if we weigh carefully the significance of the wing structure, 
especially its tracheation and musculature and we have absolutely 
no evidence in parallel structure or otherwise of such actual 
history. 
On the other hand the chief difficulty in the theory of aquatic 
origin, the difficulty which for a long time seemed to me to in- 
