

''-:.;'.-..:- :-::' 



B 



FIG. 12. Later stages in the formation of the blastoderm. A, newly 

 formed blastoderm, from a sagittal section, cell boundaries just appearing. 

 B and C, blastoderm cells dividing obliquely. D, blastoderm cells so ar- 

 ranged that their nuclei lie at two levels. E, blastoderm cells from 

 ventral side of egg, 24-26 hours. F, same, 28-30 hours, x 1107. 



