116 PARASITIC AMOEBAE OF MAN. 



consists of a mass of cytoplasm containing a nucleus 

 and varying in shape when in motion, although it is 

 always spherical or oval in outline when motionless. 

 The cytoplasm contains a nucleus and one or more 

 vacuoles which are not contractile. The cytoplasm 

 is divided into two distinct portions, the ectoplasm 

 and the endoplasm, the ectoplasm being clear and 

 glass-like in appearance, while the endoplasm is less 

 refractile and more granular in structure. The endo- 

 plasm contains the nucleus, vacuoles, and may con- 

 tain red blood corpuscles, bacteria, crystals, or other 

 material which may have been engulfed by the para- 

 site. The nucleus is generally invisible and contains 

 a very minute karyosome. Movement is accom- 

 plished by the extension and retraction of very 

 distinct pseudopodia formed by the ectoplasm. Re- 

 production occurs by simple division and by sporula- 

 tion or gemmation. 



The following detailed description of the mor- 

 phology of this parasite is the result of careful study 

 of many thousand of these organisms and refers only 

 to the morphology of the amoebse as they are observed 

 in the feces. I have not been able to obtain cultural 

 forms of this parasite, although some authorities have 

 claimed to have done so. 



Size. The size of Entamoeba histolytica is 

 variously stated by different observers, but it may 



