188 PARASITIC AMCEBJE OF MAN. 



of the nucleus, followed by the division of the cyto- 

 plasm, resulting eventually in the production of two 

 amoebse. Mitosis is of a primitive type, but in well 

 stained specimens, especially if the iron hsematoxylin 

 method be used, mitotic figures are frequently 

 observed. The karyosome first divides, followed by 

 the division of the nucleus. 



Reproduction in a cyst is preceded by cyclical 

 changes in the nucleus. These changes have been 

 well described by Hartmann, who states that in no 

 other species of amoeba has he observed such clear 

 cyclical changes in the karyosome. Wet-fixed prepa- 

 rations, in sublimate alcohol, and stained with iron 

 hsematoxylin should be used in studying the nuclear 

 changes. 



Prior to encystment the karyosome apparently 

 becomes differentiated into distinct portions, a net- 

 work composed of refractile fibres which contains 

 within it a clear fluid-like substance. The clear area 

 surrounding the centriole gradually disappears and 

 prior to division the nucleus appears to be composed 

 of a delicate network upon which are arranged minute 

 masses of chromatin which appear highly refractile 

 in the living specimen. 



As these changes are occurring in the nucleus the 

 organism extrudes all foreign matter, becoming hya- 

 line in appearance and spherical in shape. The nucleus 



