AMCEBJE OF THE INTESTINAL TRACT. 183 



Size. This parasite is slightly smaller than Enta- 

 mceba histolytica measuring from 15 to 45 microns 

 in diameter, while the cysts measure From 7 to 12 

 microns in diameter. The size is of no value in the 

 differentiation of the species because the organisms 

 resemble in this respect both Entamoeba coli and 

 Entamoeba histolytica. 



Shape. When at rest the organism is spherical 

 in shape, but great variations in its contour are ob- 

 served when it is in motion. 



The Protoplasm. As in other amoeba? the ap- 

 pearance of the protoplasm varies with the age of 

 the organism. The very young amoebae show a 

 distinctly granular protoplasm in which there is a 

 well defined nucleus. In the older amoebae the proto- 

 plasm appears still more granular and in almost 

 every instance a definite nucleus having a strong 

 nuclear membrane is observed. The ectoplasm can- 

 not be distinguished when the parasite is motionless, 

 but it is very distinct when motility is present. 



The Cytoplasm. When fully developed the cyto- 

 plasm of Entamoeba tetragena presents two well de- 

 fined portions, an outer, the ectoplasm, and an inner, 

 the endoplasm. This distinction is not evident unless 

 the organism is moving, but in such instances it will 

 be observed that the pseudopodia formed of ecto- 

 plasm are composed of material distinctly different 



