130 



J. Thomas Patterson. 



20 



21 



Fig. 20. — A seventeen-celled stage, drawn from a whole mount preparation. 

 The egg was taken from the isthmus between four and five hours after fer- 

 tilization. The blastoderm is remarkable in that it has many short radial 

 furrows situated near the margin of the primary area (see text for a de- 

 scription of these furrows). X IS. 



Fig. 21. — A fifteen-celled stage, drawn from the living egg (see Table 1, 

 hen No. 5). a — h, plane of section shown in Fig. 22. x 18. 



e^ 



o •;■•.■; ■' »,»«»,» A ■••'•.••.!•.•*• ■.•■.•. .••■.■-■.■■: 



22 



Fig. 22. — Section through plane o- 

 X 55.5. 



-Z>, Fig. 21. S.G., segmentation cavity. 



