PLATE 19 



EXPLANATION OF FIGURES 



95,96 (1150) Centrifuged 15 minutes in 4-cell stage, fixed at once. In figure 

 95 the axis of centrifuging was parallel with the first cleavage plane, in figure 96 

 at right angles to it. Cytoplasm, nuclei and centrospheres have been displaced 

 from the animal pole by yolk in two of the other cells, but so far as possible the 

 centrospheres remain between the nuclei and the polar bodies. 



97, 98 (1038) Centrifuged 100 turns of hand machine during third cleavage, 

 fixed 15 minutes later. The axis of centrifuging was parallel with the first cleav- 

 age plane. The spindles are normal though the}' have been somewhat displaced 

 from their typical positions. 



99 (1145) Centrifuged 4 hours in 4-cell stage, fixed at once. Cytoplasm, 

 nuclei and centrosomes were displaced to the vegetal pole, and the third cleavage 

 spindles which were present in the cells are so placed that large yolk-rich micro- 

 meres will be cut off at the animal pole. 



100 Centrifuged k hour, fixed at once. Centrifuging took place during the 

 third cleavage so that two of the micromeres (Ic, Id) were formed at some distance 

 from the animal pole. Lobe (L), containing oil, marks the centripetal pole. 



410 



