614 



CAUDM. GILLS OP ZYGOPTERID LARV^I?:, 



primary and secondary internal laminse begin to develop. It is 

 also possible, in some sections, to make out the main longitudinal 

 nerves, which do not appear to differ in position from those of 

 the drills in the fullv srown larva. 



Text-fig. 41. 

 T..S. through caudal .i^ills of AtiMrowirion cyaiit Selys, sixth instar. at 

 about half-way along the gill. Lctteriii'g as in Text-fig.oT: h, hair; 

 IL internal lamina; nr, main nerve; ( x 870). 



Structure of the Gills in the Seventh Instar. 



In this stage, the gills only differ from those of the Sixth 

 Instar by their slightly broader lamellar form, and by the more 

 definite formation of the internal laminae, together with the first 

 beginnings of the alveolar meshwork. Having reached this 

 stage, the gill contains all its essential structures. Further de- 



