PLATE S 



EXPLANATION OF FIGURES 



23 and 24 Sections through the 16-celled eggs, Nos. So (11) b and 85 (11) a, 

 respectively, to show the relative distribution of yolk granules within the blasto- 

 meres and in the cleavage cavity. As in figures 19-22 the blastocyst formation 

 is anticipated. The blastocyst will be completed when the gaps (i, i) have been 

 filled by the continued flattening and multiplication of the cells (X 390). 



25 Section of 52-celled completed blastocyst, No. 50 (3) a, showing included 

 deutoplasm and coagulum in cavity. The large cell in upper portion of figure 

 is one of four retarded blastomercs situated at this pole (X 563). 



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