PLATE IG 



EXPLANATION OF FIGURES 



79 (1145) Centrifuged 4 hours, fixed 6 hours hitcr. Cytophism and nuclei 

 were displaced toward the vegetal pole and the first cleavage was nearly equa- 

 torial, while the second cleavage was meridional. In the four macromeres thus 

 formed the original polarity is preserved as far as possible and micromeres are 

 being formed on the sides of the cells toward the polar bodies. 



80 (1136, 5) Centrifuged 30 minutes, fixed 7 hours later. The first cleavage 

 (/) was oblique as in figure 65; the second was meridional, being at right angles 

 to the first in the lower cell and parallel with it in the upper one. The lower 

 cells contain most of the cytoplasm and give rise to the micromeres of the first 

 set which are reversed in position; the upper cells which contain little cytoplasm 

 have not yet formed micromeres. 



81 (1032A) Centrifuged 2h hours, fixed 21 hours later. Cytoplasm and 

 nuclei were displaced toward the vegetal pole, the first cleavage Avas nearly 

 equatorial, and the second nearly meridional. Each of these macromeres has 

 formed a micromere of the first quartet around a point, about 90° from the polar 

 bodies, which constitutes a new animal pole; the two lower macromeres are bud- 

 ding off micromeres of the second quartet. 



82 (1090) Centrifuged 100 turns of hand machine, fixed 16 hours later. 

 The lower half of the egg is developing normally; the upper half is abnormal and 

 is difficult to interpret. 



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