294 THE PATHOGENIC RHIZOPODA 



A transition from the free living to the cell infesting rhizopods is 

 afforded by one species of shelled forms — Chlamydophrys stercorea — 

 and by different species of ameba — Entameba coli and Entameba 

 histolytica — the life activities in all being singularly in conformity with 

 the examples given above. 



Chlamydophrys stercorea, first described by Cienkowsky in 1876, is 

 a rhizopod provided with a transparent glass shell of silica, found in 

 animal feces. From its type of pseudopodia it would be classed with 

 the reticulosa rather than with the lobosa or ameba type, and comes 

 closer, therefore, to polystomella than to arcella or centropyxis. 

 Schaudinn (loc. cit) found it in the feces of many different mammals, 

 including cow, guinea-pig, turtles, and man, and was able to follow its 

 life history by infecting his own digestive tract with encysted forms 

 of the organism. 



The protoplasm of the cell contains one nucleus, many fine par- 

 ticles, which are destined to form the shell of the daughter individual, 

 contractile vacuoles (one or more), and idiochromidia in the form of 

 a densely packed mass of granules about the cell nucleus. Like 

 arcella, centropyxis, euglypha, and other shelled rhizopods, the organ- 

 ism reproduces asexually by budding division, the plasm flowing out 

 of the shell opening until a daughter mass is formed equal in size to the 

 parent; the nucleus then divides by mitosis, one-half passing into the 

 bud organism. The idiochromidia do not flow into the daughter 

 protoplasm with the protoplasmic streaming, as in euglj'pha and 

 centropyxis, but adhere to the nuclear membrane, so that when the 

 nucleus divides, the germ plasm is likewise divided into two parts, the 

 daughter organism thus getting its proportion of the important idio- 

 chromidia. The sexual development is quite different from that of 

 centropyxis. There is no dimorphism, and whereas in centropj'xis 

 the idiochromidia-bearing swarmers move out of the shell, leaving 

 the disintegrating primary nucleus and residual protoplasm in control 

 of the parental abode, here the residual parts are thrown out of the 

 shell opening and the idiochromidia remain in the shell. The idio- 

 chromidia next give rise to a small number of secondary nuclei, usually 

 eight, by segregation of the chromatin granules, and the protoplasm 

 then divides into as many parts as there are nuclei. Each part assumes 

 an oval form, develops two flagella at the pole, and swims out of the 

 shell and away. Two swarmers (flagellispores) from different ances- 

 tors fuse, form a hard, protecting cyst which becomes brown in color 

 and irregular in contour, and within these the fertilized cells with a 

 high potential of vitality, live until conditions are again suitable for 

 development. With characteristic patience and ingenuity Schaudinn 

 kept these cysts in damp chambers for a period of many months 

 without observing any change, and finally inoculated himself: "I 

 swallowed on November 17, 1899, for the first time, the contents of 



