DEVELOPMENT 



123 



respond to the segments of the germ band. Each neuromere consists of 

 a pair of primitive ganglia, and these are connected together by paired 



FIG. 198. Diagrammatic sagittal sections to illustrate invagination of germ band in 

 Calopteryx. 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. 199. Diagrammatic sagittal sections to illustrate revolution of Calopteryx embryo, 

 a, antenna; aw, amnion; /, labium; W 3 , thoracic legs; m, mandible; mx, maxilla; s, serosa. 

 After BRANDT. 



nerve cords, which later may or may not unite into single cords; more- 

 over, some of the ganglia finally unite to form compound ganglia, such 



