PLATE 6 



EXPLANATION OF FIGURES 



11 and 12 Two sections of 4-celled egg No. 81 (5), showing relative position 

 of the two pairs of blastomeres. The configuration of the shell membrane iSM) 

 and the mass of albumen (ALB) will enable the reader to determine the axes of 

 the pairs of blastomeres. It will be noted that these are nearly parallel (X 125). 



13 and 14 Two sections of 4-celled egg No. 81 (11). The blastomeres have 

 shifted more than those of figures 11 and 12 (text figure 1 B). The cells are rela- 

 tively small (X 125). 



15 and 16 Two sections of 4-celled egg No. 81 (5), showing the two pairs of 

 blastomeres almost at right angles to each other. Compare text figure 1 A 

 (X 125). 



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