March, 1916.] CraMPTON : OrIGIN OF WiNGS. 7 



tracheal gills (sucK as those found on the abdomen of immature 

 Ephemeridie), that his name is usually associated with the theory 

 ascribing the origin of the wings to the tracheal gills. Many subse- 

 quent investigators have accepted his views, wholly or in part, and 

 have endeavored, with varying success, to overcome the objections 

 to the theory in question. Among the supporters of the theory of the 

 tracheal-gill origin of the wings of insects may be mentioned Landois 

 (1871), Lul)bock, (1873), Graber (1877), Palmen (1877), Hofmann 

 (1879), Adolph (1879-1881), Brauer (1885), Cholodkovsky (1886), 

 Redtenbacher (1886), Lang (1888), Verson (1890), Simroth (1891), 

 Pratt (1899), Osborn (1905), Woodworth (1906), J. A. Thomson, 

 and many others. Cholodkovsky (1886) also thinks that the wings 

 are homologous with the prothoracic patagia^ (not the tegulae) of 

 the Lepidoptera, and Walton (1901) even goes so far as to regard 

 the tegulae as wings in the process of formation ! 



Some investigators, perceiving the difficulties inherent in the at- 

 tempt to derive the wings from tracheal gills, have attempted to 

 avoid the difficulty by suggesting that the wings may not have been de- 

 rived from gills, but gills may themselves have been derived from 

 wings, or both wings and gills may have had a similar origin. Thus, 

 Redtenbacher (1886) thinks that wings and tracheal gills are homo- 

 dynamous, but " it is questionable whether the wings were derived 

 from tracheal gills, since the converse may be true ; and that wings 

 may have become metamorphosed into gills, is not beyond the realm of 

 possibility." He likewise compares both wings and gills to the pro- 

 notal expansion of Mantids, etc. 



Lang (1888) was impressed with the fact that aerial respiration 

 is clearly the primitive one in insects, and in order to derive the wings 

 from tracheal gills, suggested that insects, at first terrestrial, became 

 adapted for aquatic life; respiratory folds of the integument into 

 which tracheae penetrate, being modified into gills, and these even- 

 tually becoming metamorphosed into wings— which thus are ulti- 

 mately derived from integumental folds. 



Grassi concludes that wings and gills may be homodynamous (/. e., 



1 It is perhaps unnecessary to mention, in this connection, that the elytra 

 of Coleoptera, etc., are not homologous with the patagia or tegulae, as some 

 writers have erroneously stated is the case. Their structure and development 

 clearly shows that they are modified fore wings and nothing else. 



