THE SARCODINA 



227 



and herbs, or fruit that grows near the ground, are likely sources of infection by 

 becoming contaminated with the resting stage of the amoebae scattered on the 

 ground or in manure. In this connection the further question arises whether 

 the human entozoic amoebae are specific parasites of man or not, and conse- 

 quently whether their infective stages would be derived only from human 

 feeces, or from the excreta of other animals also. From general considerations 

 of parasitism in Protozoa, it seems probable that the harmless E. coli is a 

 specific parasite of man, but that the pathogenic 

 forms are parasites of other animals also, and 

 perhaps only occasionally find their way into the 

 human body ; in which case garden-manure might 

 be a fruitful source of contamination, through 

 the medium of vegetables habitually eaten 

 uncooked, such as lettuce, celery, etc. None of 

 these questions can be answered decisively at 

 present, however, and there is a wide field of in- 

 vestigation open. 



Greig and Wells found that in Bombay amoabic 

 infection shows a marked seasonal variation, 

 closely associated with variations in humidity, 

 but not corresponding with those of temperature, 

 and reaching its maximum in August. 



In addition to the various species of Amoeba 

 and of allied genera and subgenera, a number of 

 other genera are included in the section under 

 consideration, for an account of which the reader 

 must be referred to the larger treatises ; but two 

 deserve special mention namely, the genera 

 Pelomyxa and Paramceba. 



The species of Pelomyxa (Fig. 91) are fresh- 

 water amoebae of large size and " sapropelic " 

 habit of life (p. 14). The body, which may be 

 several millimetres in diameter, is a plasmodium 

 in the adult condition, containing some hundreds 

 of nuclei ; it is generally very opaque, owing to 

 the animal having the habit of loading its 

 cytoplasm with sand and debris of all kinds, in 

 addition to food in the form chiefly of diatoms. 

 The pseudopodia are of the lobose type, blunt and 

 rounded, but the animal may also form slender 

 reticulose pseudopodia under certain conditions 

 (Veley). The cytoplasm is very vacuolated, and 

 contains a number of peculiar refringent bodies 

 (" Glanzkorper ") of spherical form, with an 

 envelope in which bacterial organisms (Cladothrix 

 pelomyxce, Veley) occur constantly. The bacteria 

 multiply by fission in a linear series in the form 

 of jointed rods, which may branch ; as a rule 

 they have five or six joints, or less, but at 

 least two. The refringent bodies are of albu- 

 minous nature (Veley). According to Gold- 

 schmidt (57), the refringent bodies arise from the 

 nuclei when they give off chromidia ; in this 

 process the chromatin is given off into the cytoplasm, and the plas tin -basis 

 of the karyosome is left as a spherical mass which becomes the refringent 

 body. At first the plastin-sphere is surrounded by the remains of the nuclear 

 membrane, which disappears, and the refringent body grows in size. Ke- 

 fringent bodies, with their bacteria, are seen frequently to be ejected by the 

 animal during life. Bott (103), on the other hand, states that the refringent 

 bodies are reserve food-stuff, their contents of the nature of glycogen, and 



FIG. 91. Pelomyxa palus- 

 tris : a specimen in which 

 the body is transparent 

 owing to the absence of 

 food-particles and foreign 

 bodies, showing the 

 vacuolated cytoplasm 

 and the numerous nuclei 

 and refringent bodies (the 

 refringent bodies are for 

 the most part larger than 

 the nuclei) in the living 

 condition. After Greeff, 

 magnified 60. 



