A' 



Ect. 



C 



Ect 



EM. 



D' 



End. H f 



Fig. 316. To illustrate the main features of insect embryology. A, B,C, Sagittal 

 sections. A', B', C, Transverse sections through corresponding stages. 

 D, Sagittal section of embryo with germ layers present. C", Transverse 

 section through C-stage embryo in mouth region. D', Transverse section 

 through D-stage embryo. E, Transverse section through older embryo with 

 haemocoele between endoderm and ectoderm (in which nerve cord is 

 developing). The mesoblastic somite on each side has given rise to the 

 gutter-like heart rudiment, to the fat-body and to the muscles of body wall 

 and gut. Embryonic membranes, the amnion A and the serosa 5 cover the 

 embryonic rudiment. Bl. blastoderm; Ect. ectoderm; End. endoderm; 

 Exe. extra-embryonic blastoderm; F. fat-body; G.B. germ band; H. haemo- 

 coel; ///. heart rudiment; M. mesoderm; Mc. muscles; Pr. proctodaeum; 

 St. stomodaeum ; Y. yolk. After Eastham. 



