PRESIDENT'S ADDRESS 



and attempts at flight they would grow larger, until the_y 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 gTow 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 numl)er 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 inedian 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 wings 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 respiration being quite subordinate. The blood would then 

 supply the parts, and thus respiration or aeration of the l)lood 

 would be demanded. As soon as such expansions would be of even 

 slight 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 deveioped, until 

 they would become permanent structures, genuine wings. They 

 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 whicli could fly ))est, i. e., which 

 had the strongest wings, wo'uld 1)c most successful in the struggle 

 for existence. Thus also, not being so much needed in larval life 

 before the reproductive organs are develoj^ed, they would not be 

 transmitted excejDt in a very rudimentary way, as iDorhaps a mass 

 of internal indifferent cells (imaginal discs), to the larva, being 

 rather destined to develop late in larval and in ]DU]3al life. Thus 

 the development of the wings and of the generative organs wonld 

 go hand in hand, and become organs of adult life." 



That there are insuperable objections to tliis view will be 

 evident if we weigh carefully the significance of the wing structure, 

 especially its tracheation and musculature and we have aljsolutely 

 no evidence in j^arallel structure or otherwise of such actual 

 history. 



On the other hand tlie chief difficulty in the theory of aquatic 

 origin, the difficulty Avhich for a long time seemed to me to in- 



