198 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



strip lying on the ventral surface. Occasionally where one of these 

 nuclei may be seen adjacent to a yolk globule, the part nearest the nucleus 

 is ill a liquefied condition. During the next two days, with the 





r-^^-' 



:^m 











Fig. 122. — Plathemis. Sagittal section of 13-day embryo, (br) Brain, {ggl) Ventral 

 nerve ganglion. (JLu) Lumen, {prod) Proctodaeum. (stom) Stomodaeum. (wo) Outer 

 wall. {u!s) Side wall of yolk spherule (ysp). 



reduction of the yolk mass, more space is left between the yolk and the 

 lower layer. Yolk never extends into the portion of the caudal end that is 

 recurved under the ventral part of the embryo. The proctodaeum 

 elongates in this region to the point of the bend where its blind end rests 

 against the yolk mass (Figs. 120B,C). 



