174 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



distinctly separated into right and left halves and covered dorsally by a 

 single layer of cells. 



Fig. 82. — Isotoma. Cross section of thorax, (cod) Coelome. {ect) Ectoderm. 

 Middle strand of inner layer. (71c) Nerve cord, {th) Thoracic appendage. 



(mds) 



The invagination of the embryo into the yolk by buckling of the 

 thoracic section now has reached its maximum (Figs. 83, 84). The dorsal 

 organ (do) now lies in the neck region of the embryo covered laterally by 

 the body wall and in part by the serosa. The yolk is still completely 



Fig. 83. — Isotoma. 



abd4 



Embryo after blastokinesis. 

 Antenna, (do) Dorsal organ. 



(abd) Abdominal appendage, (ant) 

 (md) Mandible. 



enclosed by embryo and amnioserosa. In this stage the anterior and 

 posterior parts of the body are nearly parallel, the appendages directed 

 toward each other, only the antennae and the anlagen of the appendage 



