MITOSIS 113 



tissue-cell in the body. The number may be very large it is 

 said to be one hundred and sixty-eight in a certain crustacean 





Fig. 23- 



Diagrams representing the essential phenomena of mitosis. A , a cell with resting 

 nucleus containing a chromatic reticulum and a single nucleolus. The 

 centrosome is double and .surrounded by the centrosphere. /', the centre- 

 suincs arc separating and each is surrounded by astral rays; the chromatin 

 forms a convoluted thread or spireme. C, The spireme is broken up into a 

 number of V-shaped chromosomes, the polar spindle is formed between the 

 now widely separate centrosomes. /?, The chromosomes attached to the 

 spindle-fibres are arranged at the equator of the spindle. , division of the 

 chromosomes, which are viewed end on. /', divergence of the chromosomes. 

 G, chromosomes collecting at the poles of the spindle, the space between 

 them occupied by interzonal fibtes ; commencement of division of the cell- 

 body. //, /, complete division of the cell, and reconstitution of the nuclei. 

 In / the centrosomes are dividing preparatory to a new mitosis. Note 

 ; ,:=metaphase ; f, G = anaphase. H, 7=telophase. 



known as Artemia salina, or it may be very small, as in the 

 thread-worm parasitic in the intestines of the horse (Ascaris 

 megaloccphala). Recent researches, however, render it doubt- 



