Ill] 



THE WINGS 



55 



strengthening the wing below the nodus, either by the recession of 

 M 2 towards the nodus, and the conversion of an intermediate cross- 

 vein into the subnodus (sn) ; or else by a similar arrangement on 

 the part of the radial sector, the basal piece of which forms, in 



Fig. 19. Phylogeny of the nodus. A, archaic condition with no nodal joint; 

 B-C, development of Mesophlebia-stage (subnodus absent); D E, addition 

 of subnodus and completion of normal nodus formation as seen in recent 

 Dragonflies ; F, nodal region of Telephlebia godeffroyi Selys. shewing apparent 

 prolongation of Sc. N nodus ; nc nodal cross-vein ; Sn subnodus. Original. 



Anisoptera, actually the subnodus itself. In fig. 19 A-E, I have 

 attempted to shew sufficient successive stages in the evolution of 

 the nodus to make the phylogeny clear. 



There only remains for discussion the case of the apparent 

 prolongation of Sc through the nodus. Fig. 19 F shews the actual 



