350 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



of insects (Fig. 311). The splanchnic layer of the mesoderm and the 

 mid-gut epithelial strands soon broaden, growing around the yolk. The 



irich 



Fig. 311. — Diacrisia 

 Inner fold of amnion, 

 (nc) Nerve cord, 

 cell, {y) Yolk. 



Cross section through posterior end of 82-hour embryo, {am) 



{hi) Blood cells. (/) Fat body, {malp) Malpighian tubules. 



{prod) Proctodaeum. {tr) Tracheal invagination, {trich) Trichogen 



two ribbons of the mid-gut epithelium fuse ventrad of the yolk (Fig. 

 312, mge) ; at 84 hours and a little later the strips of mesoderm also fuse. 



malp 



Fig. 312. — Diacrisia Cross section of abdomen of S4-houi embryo, {am) Amnion. 

 {hi) Blood cells, {g) Gonad, {malp) Malpighian tubules, {mge) Mid-gut epithelium. 

 Inc) Nerve cord, {oen) Oenocytes. {splm) Splanchnic mesoderm, {trich) Trichogen cell. 



Shortly after the embryo rotates on its longitudinal axis, both these 

 layers have met and fused on the dorsal side. The fat body developing 



