PLATE 17 



EXPLANATION OF FIGURES 



83 (1040) Centrifuged 10 minutes in 1-cell stage, fixed 5^ hours later. De- 

 velopment delayed; cytoplasm and cleavage spindle near vegetal pole. In the 

 right hand cell a karyomere (km) which has not yet fused with remainder of the 

 nucleus. The polar bodies lie a little to one side of the cleavage furrow. 



84 (1038) Centrifuged 10 minutes at close of first cleavage, fixed 3 hours 

 later. Axis of centrifuging at right angles to the egg axis. Centrospheres have 

 been moved less than the cytoplasm and nuclei, indicating that they are attached 

 to the surface layer near the animal pole. 



85 (1139, 1) Centrifuged 2h hours in 2-cell stage, fixed at once. The cyto- 

 plasm and nuclei are displaced toward the vegetal pole ; the centrospheres have 

 been displaced but little from their normal positions and lie between the nuclei 

 and the polar bodies. 



86 to 89 (1037) Centrifuged 10 minutes in 2-cell stage, fixed at once. Cyto- 

 plasm, nuclei, centrospheres {Cs) and spindle remnants have been displaced 

 toward the vegetal pole in figures 86, 87, 89, toward outside in figure 88; the 

 mid body (fig. 86, MB) remains unmoved and the centrospheres (Cs) lie on the 

 sides of the nuclei toward the polar bodies. The lane of cytoplasm leading; 

 from the centrospheres to the animal pole shows that the substances of the egg 

 are not free to move according to their specific weights. 



406 



