PRESIDENT'S ADDRESS 



ence to the beautiful figiu-es and descriptions in the work of Corn- 

 stock and Xeedham just mentioned will suffice. 



Granting, however, a eommon origin for the wings of all 

 insects the problem of their original appearance, the factors in 

 development become all the more interesting. In order to show 

 the position taken by different students of the subject I beg tO' quote 

 a few paragraphs from various sources. Gegenbaur presents the 

 following: "The wings must be regarded as homologous with 

 the lamellar tracheal gills, for they do not only agree with them 

 in origin, but also in their connection with the body and in 

 structure. In being limited to the second and third thoracic 

 segments they point to a reduction in the number of the tracheal 

 gills. It is quite clear that we must suppose that the wings did 

 not arise as such, but were developed from organs which had 

 another function, such as the tracheal gills; I mean to say that 

 such a supposition is necessary, for we cannot imagine that the 

 wings functioned as such in the lower stages of their development, 

 and that they could have been developed by having such a 

 function." 



This general view is stated a little more in detail by Lang : "The 

 problem of the phylogenetic origin of the wings of insects is extreme- 

 ly difficult and as yet by no means solved. The rise of such organs 

 is not explained by saying that they are integmnental folds, which 

 gradually increased in size, stood out from and eventually articu- 

 lated with the body. The wings must in all stages of their 

 phylogenetic development have performed definite functions. It is 

 impossible that they were originally organs of fligiit. What 

 function it was that they performed before they became exclusively 

 organs of flight, is, however, entirely a matter of conjecture. The 

 following view is at present the most acceptable. (1) The an- 

 cestors of the Hexapoda were, like the now living Apterygota, 

 wingless land animals breathing through tracheae. (2) The 

 Apterygota-like ancestors of the Pterygotan racial group became 

 aclapted to living in the water. Dorsal integumental folds served 

 for breathing in the water. The rise of such respiratory folds 

 offers no difficulty, since every increase of surface, small or large, is 

 of service. (3) The respiratory appendages (into which the trachea 

 were continued) became movable and may perhaps have assisted in 

 locomotion (swimming). This assumption also offers no difficultv, 

 since the gills of many aquatic animals are movable, and their 

 power of moving is an advantage on account of the exchange of 

 water thus caused. (4) In a new gradual change to land life the 

 respiratory function became less important and the locomotory 

 function came. to the front. Here, however, lies the greatest dif- 

 ficulty. It may, however, be assumed that the animals, while still 

 living in water were capable of gliding over the surface of the 

 water by tlie swinging of their branchial leaves, just as flying fish 



