220 PARASITIC AMOEBAE OF MAN. 



sites become motionless; the flagellum disappears; 

 the border of the spherical body remaining begins to 

 undulate; and eventually a blunt, well defined pseu- 

 dopodium appears, and the parasite enters on its 

 amoebic stage of existence. 



The morphology of Paramceba hominis varies 

 greatly in its different stages of development and 

 for this reason it will be necessary to describe the 

 morphology of each stage, i.e., the amoebic stage, the 

 encysted stage, and the flagellate stage. 



The Amoebic Stage. In this stage the parasites 

 measure from 10 to 25 microns in diameter, the aver- 

 age measurement being from 18 to 20 microns. 

 Amoeboid motion is first apparent as an undulatory 

 movement of the periphery of the parasite followed 

 by the projection of small, bluntly conical pseudo- 

 podia, in those organisms which have originated from 

 the flagellate forms, but in those amoebae which re- 

 sult from simple division, amoeboid motion is first 

 manifested by the projection of pseudopodia. In the 

 younger organisms amoeboid motility is very slug- 

 gish, progressive motion being absent, as a rule, 

 although the pseudopodia may be projected and with- 

 drawn with considerable rapidity; in the larger and 

 older amoebae progressive motion is quite marked, the 

 ectoplasmic pseudopodia being projected rapidly and 

 the endoplasm flowing into them immediately. 



