NO. 1331. 



DRAGON-FLY WING VENATION— NEEDHAM. 



709 



II. THE STUDY OF THE WING BY AREAS. 



These three points of transverse bracing- are also the points about 

 which have phxyed the forces wliich have evolved tlu^ dragon-fly wing. 

 They are the points about which one can best follow the shifting of 

 veins and trachetv. In a study of genealogy one can hardly do l)etter, 

 therefore, than to discuss the wing by areas with these points as 

 centers, drawing freely upon ontog-eny, comparative anatomy, and 

 paleontology for evidence of the changes that have taken place. 



THE AREA OF THE STIGMA. 



The stigma is developed upon the cutting edge of the wing at the 

 point of greatest impact against the air. It would seem to serve the 



Fig. 4.— Ptero.stigmas; p, ok Aikix jimiiis Oiury; 7. ok Minthiiria innreclln Sei.ys: r, ok Nro(jo»iplius 

 iiii}lciitug Sklys; s, of Uropetala carovci Selys; t, ok Ayrion mcrcurinlc CHARrE.VTiER: «, of Anoma- 

 laurion liasfatitm Say; v, of Tliorc gUjanlea Selys; xv, of Mccisloyagtcr liicniia Dri'KY; .r, Calopleri/j: 

 maciihtta BKAVXoiti; //, MicioKtifiiiia si''!; z, Mkruatiiima riilundafHiii, Ski.ys, iiink win(;. 



double purpose of tirndy uniting Mic veins of the Front margin and of 

 iucreasiri"' the elliciiMicv of the wing stroke l)v adding weight at this 



