PARASITIC S.AliCODINA 



129 



The life history also varies in the different species, many possess- 

 ing a flagellated stage. On the basis of life history and habits 

 the old genus Amoeba has been broken into a number of genera, 

 seven according to Calkins. Of these only three occur as para- 

 sites of man. 



The amebse which are especially adapted to live as parasites 

 in the bodies of animals belong to at least two distinct genera, 

 Endamoeba and Craigia (or Paramoeha). Endamoeha includes 

 amebae of large size which are not readily distinguishable from 

 the free-living genera except in their parasitic manner of life 

 and by the fact that they will not grow in pure cultures. Craigia 

 includes parasitic species of amebse which, like some free-living 

 forms, pass through a stage 

 in which they possess flagella 

 and resemble true flagellates. 

 In addition to these, the 

 genus Vahlkatnpfia includes 

 species which may tempo- 

 rarily live as parasites in man 

 if accidentally swallowed. 

 They are minute in size, nor- 

 mally free-living, and have 

 no flagellated stage of devel- 

 opment. A few species are 

 true parasites of cold-blooded 

 animals. Belonging to the 

 Sarcodina also, but not 

 closely related to the amebae, 

 is a peculiar parasite, Chlamydophrys stercorea (Fig. 35), found in 

 freshly passed fseces of a number of animals, including man. It 

 has a transparent glassy shell of pseudochitin, through the mouth 

 of which it protrudes its slender pseudopodia. 



The number of distinct species of Endamceha which Uve in the 

 human body is still a matter of dispute. Due largely to the work 

 of Darling in disentangling the species of amebse only two are 

 now usually recognized as habitually inhabiting the human 

 intestine. One of these, E. coli, is a very common but ap- 

 parently harmless resident, while the other, E. histolytica, is a 

 bandit of the first order, and the cause of amebic dysentery and 

 liver abscess, diseases of great importance in tropical countries. 



Fig. 35. Chlamydophrys stercorea, show- 

 ing portion of protoplasm of body (prot.) 

 and slender anastomosing pseudopodia (ps.) 

 protruding from transparent shell (sh.) ; n., 

 nucleus. X 300. (After Schaudinn, from 

 Doflein.) 



