March, I9i6.] CraMPTON : OrIGIN OF WiNGS. 9 



Termites' wings, and of Woodward (1876), who pointed out that the 

 aHform lateral expansions (paranota) of the pronotum in the fossil 

 insect Lithomantis carbonaria are homodynamous with the wings, 

 have furnished a firm foundation for the paranotal theory of the 

 origin of the wings, and this view has been accepted wholly, or in 

 part, by many subsequent investigators, among whom may be men- 

 ti&ned Huxley (1877), Haase (1886), Korschelt and Heider (1891), 

 Zacharias (1892), Krueger (1898), Packard (1898), Comstock and 

 Needham (1899), Powell (1904-1905), Duerken (1907), Lameere 

 (1900-1908), Handlirsch (1906-1908), McMurrich, and others. 



From the foregoing discussion, it is evident that the two theories 

 which have received the most widespread acceptance, are the tracheal 

 gill theory and the paranotal theory of the origin of the wings — and 

 opinion seems to be pretty evenly divided between the two. The evi- 

 dence brought forward in support of the other theories seems insuf- 

 ficient to warrant their acceptance, nor does it appeal as strongly as 

 the two mentioned above do, to our ideas of the factors and method 

 of evolution; so that it is preferable to suspend judgment upon the 

 other theories (until more evidence has been accumulated) and to 

 select as a '' working basis " one of the two theories which appear to 

 be in accord with the greatest number of known facts — in other 

 words, we must (for the time being, at least) choose between the 

 tracheal-gill theory and the paranotal theory of the origin of the 

 wings of insects. 



Unfortunately, all of the evidence bearing upon the subject is not 

 accessible to me at this time; but such of the arguments as were avail- 

 able have been brought together in the following comparison of the 

 two theories. In addition, such evidence as has suggested itself as 

 having a bearing upon the subject under discussion, has been added 

 to strengthen either side of the question impartially; and I feel con- 

 vinced that sufficient evidence is at hand, to make an unbiased deci- 

 sion in favor of one theory or the other. 



It must be admitted that the tracheal gill theory is a fascinatingly 

 clever one, and if the premises of its arguments be granted as correct, 

 the logic of its appeal is almost irresistible; but if the rival theory is 

 fully in accord with the same facts (or even more of the known 

 facts) which have been cited as evidence of the tracheal gill theory, 

 and is not open to the same objections as might be raised against this 



