PLATE 9 



EXPLANATION" OF FIGURES 



26 Section of blastocyst No. 50 (3) b, to show distribution of j'olk granules. 

 The yolk granules in the cleavage cavity are to be found chiefly within the cyto- 

 plasmic fragments and the included nucleated cell (C). Much yolk is still within 

 the blastomeres (X 540). 



27 Section of blastocyst No. 144 (1) d. somewhat more advanced than those 

 shown in figures 25 and 26 {A, text figure 6). The specimen is somewhat shrunken. 

 The non-formative area (to the reader's right) has become considerably attenu- 

 ated. A study of the series from which this section is taken shows that the 

 apparently included cells are attached to colls situated in the wall of the blasto- 

 cyst (X 375). 



78 



