362 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



on the inside the cell wall has not been completed. After they reach 



the periplasm, some of the nuclei migrate 

 back into the yolk where they become 

 the yolk cells, or vitellophags, as indi- 

 cated by DuBois (1932). 



Before the inner cell walls of the 



Fig 313 — Sciara Section of de- 

 \ eloping blastoderm, foui hours old. 

 (cc) Cleavage cells, (gc) Germ cells. 

 iy) Yolk. 



Fig. 314. — Sciara Cioss section of de- 

 veloping blastoderm four and one-half hours 

 old. {cc) Cleavage cells, (y) Yolk. 



blastodermal cells are formed, the germ cells migrate inward, passing 

 separately between the blastodermal cells (Fig. 313). They lie just inside 



'^'■^r^ 





?^ 



gc- 



'i?fiMk 



Fig. 315. — Sciara. Longitudinal section of posterior pole of egg. (gc) Germ cells, (os) 



Oosome. 



the blastoderm at the posterior end of the egg. At about the tenth hour, 

 when the germ cells and the vitellophags have completed their inward 



