t) Journal New York Entomological Society, [^oi. xxiv, 



no means certain, however, that the prothoracic islands are homo- 

 dynamous with the wing disks, and the proof offered by Plateau in 

 support of his theory seems rather inadequate. 



The observations of Pratt (1899), Tower (1903) and Verson 

 (1890-1894) might, in some measure, be taken as upholding Plateau's 

 theory that the wings are modified spiracles. Thus Tower (1903) 

 states that when the mesothoracic spiracle migrates forward, " the 

 spiracle alone migrates, and the thickened area of the hypodermis 

 remains and probably becomes the fundament of the elytron." Powell 

 (1905), however, combats the idea that the wings develop from the 

 discs of the degenerated spiracles of the meso- and metathorax, and, 

 in opposing Tower's statements, asserts that in some Coleoptera the 

 spiracles have not migrated forward, and that the wing primordia (or 

 fundamentals) arise distinctly above or below the positions occupied 

 by the thoracic and abdominal spiracles. He therefore concludes that 

 Tower's conclusions in this matter are incorrect, and the fact that 

 his investigations were made in the same order of insects (Coleop- 

 tera) studied by Tower, should have considerable weight, especially 

 since he sought to verify Tower's work in carrying out his own in- 

 vestigations. 



Many investigators, even in modern times, have advocated the der- 

 ivation of wings from tracheal gills. Owen (1848) supports the idea 

 promulgated by Oaken (1831) that the wings are modified gills, such 

 as are born on the tergal region of Annelids, and Ganin (1869) as- 

 ascribes a respiratory function to the wings. 



Carus (1839) states that in the "immature Agrion pncUa, the 

 blood circulates in the forming wings exactly as in gill plates, and it 

 would be difficult to find a more perfect demonstration of the fact that 

 the wing is a modified gill" {teste Plateau, 1871). 



Enderlein (1902) suggests that since the ancient pterygote insects 

 lived in an atmosphere of great humidity, they may have used their 

 wings as a sort of "gill" (since the wings are supplied with tracheal 

 branches in the early stages of development), but does not enter into 

 the controversy as to whether the wings were derived from the 

 tracheal gills of Ephemerid nymphs, or not. 



Gegenbauer (1870-1878), who regards the wings of insects as de- 

 rived from the dorsal gills of their Annelidan ancestors, has done so 

 much to clearly formulate the theory that the wings are modified 



