634 GRIFFIN. 



EXPLANATION OF PLATE XXXIV. 



(Zirphaea crispaia.) 



Fig. 47. Unfertilized egg, showing ring-like chromosomes and double nucle- 

 olus. 



Fig. 48. Asters pushing in the wall of the germinal vesicle ; chromosomes 

 persistent. 



Fig. 49. Later stage, with the chromosomes entering the spindle. 



Fig. 50. Fully formed first polar amphiaster ; the discarded mass of nuclear 

 chromatin at w. 



Fig. 51. Later stage, the chromosomes pulling out into rings. 



Fig. 52. Anaphase ; chromosomes diverging as daughter-V 's. 



Fig. 53. Second polar amphiaster, showing double chromosomes. / p. b., 

 first polar body. 



Fig. 54. Second polar telophase. J, sperm-nucleus and aster. //.*., first 

 polar body ; 2 p. b., second polar body. 



Fig. 55. Slightly later stage ; chromosomes becoming vesicles. 



Fig. 56. Approach of sperm-nucleus to the fusing egg-vesicles ; persistent egg- 

 centrosomes. 



Fig. 57. Egg-nucleus and centrosome. 



Figs. 58-60. Approach of germ-nuclei and divergence of centrosomes. 



Fig. 61. Transverse section through equatorial plate of first cleavage-figure, 

 showing separate paternal and maternal chromosome groups. 



Fig. 62. Two-cell stage. 



Fig. 63. Same, preparing for division. 



Fig. 64. Blastula. 



