PLATE 12 



EXPLANATION OF FIGURES 



59 to 82 Centrifuged after both maturation divisions but before the comple- 

 tion of the first cleavage. 



59 (1088) Centrifuged 100 turns of hand machine, fixed 1 hour later. Side 

 view of an egg in which the axis of centrifuging was at right angles to the polar 

 axis. Egg nucleus connected by strands of spongioplasm with the animal pole. 



60 (1037) Centrifuged 10 minutes, fixed at once. Yolk was thrown to the 

 animal pole, oil and cytoplasm to the vegetal pole. Both germ nuclei are stretched 

 out in the direction of centrifuging and both have been pulled away from the 

 animal pole. The egg nucleus is still connected with that pole by strands of 

 granular cytoplasm (spongioplasm) and there is an aggregation of this immedi- 

 ately under the polar bodies ; other strands run through the zone of spongioplasm 

 and of liquid yolk into the zone of yolk spherules. 



61 (1037) Centrifuged 10 minutes, fixed at once. The germ nuclei and 

 cytoplasm are displaced somewhat from the animal pole and the nuclei are 

 distorted. 



62 (1139, 1) Centrifuged 2\ hours, fixed at once. Both germ nuclei to- 

 gether with the cytoplasm have been forced away from the animal pole. 



63 to 65 (1037) Centrifuged 10 minutes, fixed at once. The first cleavage 

 3pindle in the anaphase has been forced away from the animal pole, the spindle is 

 more or less distorted and the centrosomes and spheres are turned toward 

 the animal pole. The lobes (L) containing oil at the centripetal pole indicate 

 that the centrifugal force was strong. 



396 



