March. 1916.] CrAMPTON : ORIGIN OF WiNGS. 23 



working hypothesis, in the following discussion of the nature of the 

 wings : 



Despite the contentions of Landois, 1874, Ganin, 1876, and Graber, 

 1889, practically all embryologists have accepted the view that the 

 wings of insects are of hypodermal origin, but whether they are 

 tergal, or pleural (or both) in nature, is still an undecided question. 

 In the paranota of Arthropods in general, these integumental out- 

 growths appear to be of a tergal nature — at least the dorsal lamella 

 of the paranota is apparently a continuation of the surface of the 

 tergum. So too, the upper surface of the developing wing of the 

 BlattidjE and other primitive winged insects appears to be a direct 

 continuation of the tergum. The view that the wings are merely 

 lateral expansions of the tergum has been strongly combated, how- 

 ever, and it is necessary to appeal to the evidence afforded by em- 

 Ijryology. The following views have been put forth by those who 

 have studied the development of the wings. 



According to Tower, 1903, Rehburg, 1886, and Palmen, 1887, the 

 wings are pleural in origin. Mayer, 1876, also states that the wings 

 are not purely dorsal, but are lateral outgrowths of the body wall. 



Powell, 1905, states that in the Coleoptera "the wing arises on 

 the pleurum at or near the future position of the dorso-lateral suture 

 (i. c, the suture between the tergum and pleuron) as a thickening 

 of the body wall which in the simplest type begins as a simple pro- 

 jecting outward and downward of this thickening." He also states 

 that "wings have been derived as lateral outgrowths or folds of the 

 hypodermis of the pleurum or tergum or both.'' 



Comstock and Needham, 1898-1899, state that the wings "appear 

 at a time when the tergum and pleura are very little chitinized and 

 are hardly more identified with one than with the other," and that 

 they arise "at the point where the suture between the tergum and 

 pleura later develops." Calvert, 1893, thinks that in the Odonata, 

 the upper lamina of the wing is tergal, and the lower one pleural. 



Marshall (1913) states that in the Trichoptera, "each wing rudi- 

 ment is situated under the dorsal plate (/. c, tergum) a little above 

 its lateral margin," and would thus indicate that the wing is tergal in 

 origin. Later, however, " it would appear that when the wing be- 

 comes external, its position would be between the tergum and 

 pleurum." Packard (1898) from his observations on the develop- 



