123 



Eight hours later, when the entoderm has completely penetrated the sub- 

 germinal cavity and obviously is growing at a much slower rate, only 

 1.79 per cent of its cells are undergoing amitosis, while mitosis has in- 

 creased to 4.49 per cent (ser. 328). 



During the period covered by series 256, 328, and 189 the growth 

 of the ectoderm is relatively slow, and in each case mitosis greatly 

 exceeds amitosis. 



13 



16 



17 



20 



24 



Figs. 13 — 18. All from a blastoderm in a mid-cleavage stage (20 hrs. old). Figs. 

 13 — 16 is a series of mitotically dividing cells, Figs. 17—18 nuclei in amitosis. 



Figs. 19 — 24. All are from mesoderm of a blastoderm taken seven hours after in- 

 cubation. See text for descriptions of Figs. 19—22. Fig. 23 shows a nucleus with 

 one half staining deeper than the other. Fig. 24 is an early prophase stage. 



