DEVELOPMENT 



153 



Tracheae. The tracheae begin as paired in vacillations of 

 the ectoderm (Fig. 201, t) ; these simple pockets elongate and 



FIG. 197. 



Diagrammatic sagittal sections to illustrate invagination of germ band in Calop- 

 tcry.v. a, anterior pole; ac, amnion cavity; am, amnion; b, blastoderm; d, dorsal; 

 g, germ band; h, head end of germ band; p, posterior pole; s, serosa; v, ventral; y, 

 yolk. After BRANDT. 



FIG. 198. 



Diagrammatic sagittal sections to illustrate revolution of Calopteryx embryo, a, 

 antenna; am, amnion; /, labium; f 1 -/ 8 , thoracic legs; m, mandible; mx, maxilla; s, 

 serosa. After BRANDT. 



