204 PARASITIC AMOEBAE OF MAN. 



The Nucleus. This structure is always well de- 

 fined and is remarkable for its richness in chromatin 

 and for its regularly spherical form. A minute karyo- 

 some can be distinguished containing a collection of 

 fine granules which are situated at the centre, form- 

 ing a centriole. In the vegetative stage the diameter 

 of the nucleus does not exceed 2^ to 3 microns, but 

 in the cystic stage the diameter of the nucleus is from 

 4 to 6 microns. The chromatin is collected at the 

 periphery of the nucleus, thus giving rise to a very 

 solid, refractive nuclear membrane. During repro- 

 duction the chromatin is scattered throughout the 

 nuclear substance and becomes arranged in threads 

 and granules. In some instances a wreath of 

 chromatin granules may be observed surrounding the 

 minute centriole. 



Vacuoles and Contained Bodies. A contractile 

 vacuole has not been observed in this species, and 

 very frequently vacuoles are absent, even in well 

 developed organisms. A single vacuole is most fre- 

 quently observed, but there may be two or three, 

 especially in organisms undergoing division. This 

 species is phagocytic for red corpuscles and also for 

 certain parasites occurring in the feces. Elmassian 

 states that he has observed Chlamydophrys stercorea 

 within amoebae of this species. Like other amoebae, 

 this organism often contains bacteria and crystals of 

 various kinds. 



