218 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



lively large, having before this practically ceased to divide. The hind 



end of the embryo pushes back over the posterior end of the yolk mass just 

 beneath the serosa; the head end remains 

 fixed (Fig. 134). The embryo, which in this 

 stage is not yet segmented, has acquired 

 broad cephalic lobes. With the increase in 

 length, the amnion becomes thinner and 

 membranous, and. the inner layer of the 

 embryo by proliferation of its cells increases 

 ;er in size (Fig. 135^), especially at the posterior 

 end. 



Soon the first traces of segmentation and 

 appendages appear. The antennae have at 

 this time become evident as backward proc- 

 esses of the cephalic lobes, postoral in posi- 

 tion, appendages of the other anterior 

 segments as far back as the thoracic segments 

 arising about the same time. There are no 

 macrosomites such as have been described 

 for Stenohothrus. When the caudal end of 

 the embryo has pushed forward along the 

 dorsal surface of the yolk almost to the 

 anterior end of the egg, three additional 



segments (meso- and metathoracic and the first abdominal) have been 



added (Fig. 1355). 



Fig. 134. — Eutermes. 

 segmented germ band. 

 Amnion, (ser) Serosa. 



Un- 

 (am) 



Fig. 135A. — Eutermes. 

 cavity, (ect) Ectoderm. 

 Yolk cell. 



Median sagittal section, (am) Amnion, (am. cav) Amniotic 

 (mes) Mesoderm, (post) Posterior end of germ band, (yc) 



As the embryo increases in length, the caudal end sinks slightly into 

 the yolk by a flexure much like that of the dragonfly. Appendages 

 increase in length; the abdomen becomes segmented; stomodaeum and 

 proctodaeum are formed; and the body walls grow dorsad. The ento- 



