This document summarizes information about the parasite Entamoeba histolytica: - E. histolytica lives in the mucous and sub-mucous layers of the large intestine in humans and can occasionally infect the liver, lungs, brain, and spleen, causing ulcers. - It has no fixed shape and size, with a spherical nucleus and cytoplasm that can be divided into a clear ectoplasm and granular endoplasm containing red blood cells. - It multiplies by binary fission and has the ability to encyst, developing a protective cyst wall prior to dividing its nucleus. - E. histolytica commonly exists harmlessly in the intestine but can invade tissues