PLATE 3 



EXPLANATION OF FIGURES 



13 (1125, 1) Centrifuged 10 minutes, fixed at once. The first polar body 

 was formed, before centrifuging, at the original animal pole; this was the cen- 

 trifugal pole and consequently the yolk was thrown to this pole while the cyto- 

 plasm was forced to the vegetal pole; the half of the first maturation spindle 

 left in the egg remains attached to the animal pole by the spindle fibers. 



14 to 18 All from same slide (1125, 2); centrifuged 10 minutes, fixed U hours 

 after. Centripetal pole marked by oil droplets. At time of centrifuging the 

 first maturation spindle was attached to the surface of the egg at the animal 

 pole and therefore was not moved; consequently the first polar body has formed 

 at that pole. The cytoplasm was displaced more or less from the animal pole 

 but is now returning, as is shown by figures 15 and 16 in which the centripetal 

 pole (marked by the oil droplets) does not lie in the middle of the cytoplasmic 

 field, and by figures 17 and 18 in which a narrow lane of cytoplasm is returning 

 to the animal pole (cf. figure 13 in which the eggs of this experiment were fixed 

 at once after centrifuging). 



378 



