342 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



in of the middle strip reduces the width of the embryo, except at the 

 head and tail ends. As development progresses, and coincident with the 



C D 



Fig. 299. — Diacrisia. A, amnion beginning to form. B, section through abdomen 

 of 34-hour embryo. C, through anterior part of abdomen of 35-hour embryo. D, through 

 neck region of 42-hour embryo, (am) Amnion, {ect) Ectoderm, {gh) Germ band. (iZ) 

 Inner layer, {ser) Serosa. 



beginning of segmentation of the ectoderm (Fig. 297C), the inner layer 

 also assumes a more segmental character. Its cells at the intervals 

 between the segments do not multiply so rapidly as in the segments 



Fig. 300. — Diacrisia. A, section through head of 42-hour embryo. B, through head 

 of 44-hour embryo, {am) Amnion, {ed) Ectoderm, igastr) Gastrula furrow, (il) 

 Inner layer. 



themselves where they form irregular layers (Fig. 302). The mass of 

 inner-layer cells at the anterior extremity is larger both in width and 



