PLATE 3 



EXPLANATION OF FIGURES 



19 The eight-celled stage. The nucleolar material is distributed to two 

 blastomeres (No.C). The polar nucleus has undergone rapid division producing 

 thirteen nuclei. Note that th« protoplasm containing the polar nuclei is gradu- 

 alh' flowing around the embryonic cells. X 620. 



20 A stage showing thirteen cells, two of which contain nucleolar material. 

 Usually there are fourteen cells, but in this case one of the blastomeres of the 

 eight-celled stage has been delayed in its division. The polar nuclei are all 

 dividing. X 620. 



21 A typical fourteen-celled stage. It is much flattened on the slide. X 620. 



22 to 24 Upper or anterior ends of three eggs showing the polar nucleus. 

 X 620. 



25 INIetaphase plate of a polar nucleus, showing the diploid number of chromo- 

 somes. , X 1827. 



20 Fii'st maturation spindle. X 182". 



27 First polar body chromatin {A) and the second oocytic chromatin (B). 

 There are eight chromosomes in each group. X 1827. 



28 The first polar body dividing (Ai and A2) and the chromatin of the second 

 oocyte. Each group has eight chromosomes. X 1827. 



29 First polar body spindle and second maturation spindle. X 1827. 



30 First and second polar bodies. X 1827. 



31 A similar stage. X 1827. 



32 Side view of a cleavage spindle of one of the first four blastomeres. X 

 1827. 



33 Polar view of the first cleavage spindle. X 1827. 



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