CHJITOGNATHA 



869 



way the two primitive cells of the testes are also pushed 

 backwards (Fig. 161 C), whereas the primitive cells of the 



Fig. 161. — Three embryos of Snaitta at the stage of the formation of the germ- 

 layers, in frontal section (after O. Hertwig, from Lang's Lehrbuch), hi, blasto- 

 pore; ltd, archenteron; g, primitive cells of the sexual organs; Dm, visceral 

 (splanchnic), pin, parietal (somatic), layer of the mesoderm ; d, fundament of the 

 mid-gut; cs, coelomic sacs ; st, stomodaj am (fore-gut). 



ovaries lie at the sides of the folds and in this way are 

 moved rather into the pair of coelomic sacs, in accordance 

 with their subsequent permanent position (Fig. 162). The 

 embryo bends more and more towards the ventral side, 

 during which a ventral ectodermal thickening becomes 



Fig. 162. -Dorsal and lateral views of an advanced embiyo of Sagitta (after 

 BuTscHLi, from BKhToua'a Compurative £mbri,ologi;). in, moutli ; al, intestinal 

 canal; vg, fundament of the ventral ganglion; ey, ectoilerm ; c.pr, c- pi alic 

 part of the boiiy cavity; so, somatic, sp, splanchnic, layer of the nicsjeieriii 

 ge, sexual oi'gaus. 



K. H. E. ' n B 



