18 



amphibians, in the 

 of plants. 



THE ANIMAL CELL [CH. II. 



cells of certain worms, or in the growing tips 



Remains of spindle. 



Line of separation of the 



two cells. 

 Antipole of daughter 



nucleus. 



Lighter substance of the 



nucleus. 



Cell protoplasm. 

 -- Hilus. 



Fie. 22. Final stages of karyokinesis. In the lower daughter nucleus the changes are still more 

 advanced than in the upper. (Waldeyer.) 



The phases may be summarised in a tabular way as follows : 



1. Resting condition of mother nucleus 



(fig. 16). 

 f 2. Close skein of fine convoluted filaments 



(fig. 17). 



| 3. Open skein of thicker filaments. Spindle 

 [ appears (fig. 18 A). 



4. Movement of V-shaped chromosomes 



to middle of nucleus, and each splits 

 into two sister threads (fig. 18 B). 



5. Stellate arrangement of V filaments at 



equator of spindle (fig. 19). 



6. Separation of cleft filaments and move- 



ment along fibres of spindle (fig. 21 A 

 and B). 



7. Conveyance of V filaments towards poles 



of spindle (fig. 21 c). 

 r 8. Open skein in daughter nuclei. 

 1 9. Close skein in daughter nuclei (fig. 22). 

 . 10. Resting condition of daughter nuclei 

 (fig. 22). 



The Ovum. 



The ovary (see Chapter LIX.) is an organ which produces ova. 

 An ovum is a simple animal cell ; its parts are seen in the next diagram. 



It is enclosed in a membrane called the zona pellucida. The body 

 of the cell is composed of protoplasm loaded with granules of food 

 material, called the yolk or vitellus. The nucleus and nucleolus are 

 sometimes still called by their old names, germinal vesicle and 

 germinal spot respectively. The attraction sphere is not shown in the 

 diagram. 



The ovum first discharges from its interior a portion of its 

 nucleus, which forms two little globules upon it called the polar 

 globules. 



NETWORK OR RETICULUM . 



SKEIN OR SPIREM 

 CLEAVAGE .... 



STAR OR MONASTER . 

 DIVERGENCE OR METAKINESIS 



DOUBLE STAR OR Di ASTER 



DOUBLE SKEIN OR DISPIREM 

 NETWORK OR RETICULUM . 



