PLATE 22 



EXPLANATION OF FIGURES 



113 to lis (1149) Centrifuged 5 hours in the 4-8-cell stage, fixed at once. 

 Figures 113 to 116 are viewed from the vegetal pole, figure 117 from the animal 

 pole. In all these cases the animal pole was centrifugal in position, the vegetal 

 centripetal; consequently the cytoplasm and nuclei of the macromeres was car- 

 ried to the vegetal pob, where a numbe- of micromeres have been formed, while 

 the first set of micromeres (ectomeres) remains at the animal pole (except in 

 figs. 113, 115, where it had not yet formed). The micromeres at the vegetal pole 

 correspond in number, contents and subdivisions to the second and third sets of 

 micromeres, but it is not certain that they give rise to ectoderm. Figures 117, 

 118 represent the same egg under a high and low focus; the stippled cells in 

 figure 117 are the first set of micromeres at the animal pole; in figure 118, the 

 second and third sets at the vegetal pole. 



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