124 



THE PROTOZOA 



C. THE NUCLEUS 



Inclosed in the protoplasm in all Mastig'ophora is a more or less 

 clearly denned nucleus. It is variable in position, and although a 

 multiple number may occur, is generally single. The structure also 



k ' 



B 



C 



E 



D 



Fig. 70. Nuclear division in Noctiluca miliaris. 



A. The first changes of the chromatin from the large karyosome condition; concentration of the substance of the divi- 

 centre (s). B. Further disintegration of the chromatin and arrangement of granules to form the chromosomes (cK). 

 imphiaster and completed chromosomes. D. The central spindle in the hollow of the nucleus; the nuclear plate of 

 mosomes is thus wrapped around the division-centre. E. A section through the centre of the long axis of the division- 

 e before division of the chromosomes. F. A section through the dividing chromosomes, c, the centrosome with 

 iting mantle-fibres. 



is extremely variable. The chromatin may be either in the form of 

 granules distributed throughout the cell and not confined by a distinct 

 nuclear membrane ( Tetramitus\ or the granules may be aggregated 

 without a membrane (Ckilomonas}, or again, the chromatin may be 



