PLATE 2 



EXPLANATION OF FIGURES 



10 Unfertilized egg showing the female pronucleus and the nucleolus at the 

 posterior end. This nucleus will form the first cleavage spindle. X 620. 



11 Egg showing first cleavage spindle in metaphase. X 620. 



12 Egg showing first cleavage spindle in anaphase. X 620. 



13 Egg showing first cleavage spindle in late anaphase. X 620. 



14 In this egg the two cleavage nuclei are reorganized and the cj'toplasm is 

 beginning to divide. The nucleolus is closely associated with one of the nuclei. 

 X 620. 



15 The two-celled stage. Note that the nucleolus is included in one blasto- 

 niere. X 620. 



16 A two-celled stage, in which the spindles are formed in preparation for 

 the four-celled stage. X 620. 



17 The four-celled stage. Only one of the four blastomeres receives the 

 nucleolar material (Xo.C). The polar nucleus is completely formed. X 620. 



IS Another four-celled stage. X 620. 



48 



