PLATE 2 



EXPLANATION OF FIGURES 



7 and 8 (1125, 1) Centrifuged 10 minutes (3000 revolutions per minute); 

 fixed at once. Anaphase of first maturation division; the spindle has been some- 

 what elongated and in figure 8 the central end of the spindle has been thrown 

 out into a lobe containing oil drops; the sperm nucleus lies in the j'olk. 



9 to 12 are all from the same slide. The eggs were centrifuged for 10 min- 

 utes, in the prophase of the first maturation division and were fixed li hours 

 later. The spindles were moved from the animal pole and during the hour and 

 a half which clasped after centrifuging the spindles advanced to the anaphase, 

 but made no progress toward the present protoplasmic pole of the egg. On 

 the other hand there are evidences that they are progressing slowly toward 

 the original animal pole which is now occupied by yolk. In subsequent stages 

 eggs of this lot show both polar bodies at the ectodermal pole and almost all 

 eggs have developed normally. This seems to indicate that in this lot of eggs 

 the first maturation spindle moves back to the original animal pole and that the 

 polar bodies are formed there. 



9 (1125, 1) First maturation spindle near the middle of the egg, on the 

 Ijoundary between yolk and cytoplasm. Sperm nucleus in cytoplasm near 

 surface. 



10 (1125, 2) Late anaphase of the first maturation mitosis. The spindle 

 lies in the middle of the egg with neither pole near the cell membrane; there is 

 no trace of cell constriction. The spindle is- apparently moving from the cyto- 

 plasm into the yolk. 



11 (1125, 2) Late anaphase of first maturation mitosis; the spindle lies in 

 the middle of the egg, almost surrounded by yolk. 



12 (1125, 2) Anaphase of the first maturation mitosis. The spindle lies 

 on the boundary Isetween the yolk and the cytojilasm and is somewhat bent and 

 distorted. 



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