Bancroft. — Distaplia occidentalis. 



PLATE 4. 



Fig. 27. Ovum in which the test cells and secondary follicular epithelium have 

 just become differentiated. Reichert j\ immers., Zeiss 3; X 1240. 



Fig. 28. Part of a half grown ovum (173 X loO/i), showing the formation of the 

 yolk, follicle, and test cells. 



Fig. 29. Selected test cells from the same ovum. 



