THE PATHOGENIC RHIZOPODA 295 



eight moist chambers, in which were innumerable permanent cysts of 

 chlamydophrys, which had lain unchanged for two or three months, 

 and found on the 20th two typical chlamydophrys in an infusion made 

 from solid feces of the 18th, while by the 24th they were so numerous 

 that every preparation contained from one to two individuals." 

 (Schaudinn, loc. cit., p. 562). When he found that the organism would 

 live in other digestive tracts, he gave up experimenting upon himself 

 and used mice. One phase in the life history of this organism was 

 earlier (1896) interpreted as a distinct species and named Leydenia 

 gemmipara. (Schaudinn, 1903, p. 563). 



Chlamydophrys, therefore, behaves Hke centropyxis and arcella in 

 its vegetative activities, but resembles polystomella more closely in 

 its formation of isogamous gametes. The chromidia are the same 

 in all, being the substance of the nuclei of the conjugating cells. 



A transition from the lumen dwelling to the intracellular rhizopods 

 is afforded by the intestinal amebse, which, since the time of Losch, 

 in 1875, have been closely associated with the problem of dysentery. 

 These are minute amebse which penetrate the tissues by forcing the 

 cells apart, and although they apparently do not enter the cells, they 

 cause destruction of the cells by cutting off the food supply, exposing 

 them to the materials of the intestine, or disturbing the ordinary pres- 

 sure relations by infiltration with round cells and edema. Different 

 observers have described many kinds of ameba in the hiunan intestine, 

 both during health and disease, and while some of these observations 

 warrant careful consideration, the majority of them are not zoologi- 

 cally satisfactory. There are few points of structure in the parasitic 

 amebse upon which to base species, and all attempts to create new 

 species on account of size differences, nature of the pseudopodia, 

 vacuoles, and the like, are insufEcient; the only safe taxonomic basis 

 is the life history, or the "individual" in the larger sense. At the present 

 time very few of the many described amebse have been followed in 

 their life history, and, although there are probably more, we recognize 

 only two species of intestinal amebse, the one, Entameba coli, regarded 

 by Casagrandi and Barbagallo, Schaudinn, Craig, and others as a 

 harmless commensal in the human intestine, and Entameba histo- 

 lytica (dysenterice, Councilman and Lafleur), regarded by pathologists 

 generally as the cause of amebic dysentery. A third form, Entameba 

 buccalis, is found in carious teeth (Prowazek). The life history in 

 both of the intestinal species was worked out by Schaudinn, and the 

 specific features were established by his demonstration of the char- 

 acteristic differences in mode of reproduction. 



Losch, in 1875, was the first to describe the simple structures of 

 these amebse, which he also was the first to regard as an additional 

 irritant, if not the cause, of dysentery. He named it Ameba coli. 

 Later observers, finding the organism in so many cases of the normal 



