THE PATHOGENIC RHIZOPODA 297 



organisms. The centronucleus, with its single division centre divides, 

 according to Schaudinn, by amitosis, but, as in the flagellates it is a 

 primitive mitosis. Spore formation is accomplished after a peculiar 

 fragmentation of the nuclear chromatin into minute granules which 

 collect in a rim around the inside of the nuclear membrane, the cell 

 body, in the meantime, throwing out all foreign matter and ceasing its 

 movements. The peripheral chromatin next collects in eight centres, 

 the nuclear membrane is ruptured, and the eight small nuclei pass 

 into the cell body. The protoplasm divides into eight parts around 

 the nuclei, and eight small amebae finally creep out. 



As with all protozoa that have been carefully investigated, the 

 reproduction by asexual means, in this case leading to auto-infection of 

 the host, cannot be maintained indefinitely, and there comes a period 

 when the organisms encyst, the conditions under which encystment 

 takes place being somewhat indefinite in Schaudinn's account. The 

 cell throws out foreign matter and products of its own metabolism, 

 and becomes more compact, smaller, and spherical, and then secretes 

 a thick and slightly refractive gelatinous membrane. The nucleus then 

 divides by primitive mitosis into two nuclei, which are separated from 

 one another by the entire diameter of the spherical cell. The idiochro- 

 midia characteristic of the rhizopods is then formed by disintegration 

 of the two nuclei, the protoplasm of the cell in the meantime dividing 

 into two incompletely separated parts around the two nuclei. In some 

 cases the entire nucleus disappears in a mass of chromidial granules, 

 in other cases there appears to be a secretion of chromidial substance 

 as in arcella, but in all cases a part of the nuclear material is thrown 

 out of the nucleus to degenerate, and this portion represents the 

 eliminated and unused nuclear parts of the free living rhizopods. 



The fertilization process, following this preliminary division of the 

 nucleus, is autogamous and similar to that in Ameba protcus and in 

 the heliozoon actinospherium, as observed by Hertwig. The organism 

 fertilizes itself in the following remarkable manner, the processes of 

 maturation recalling those of the ciliate paramecium: 



From the disintegrated chromatin or idiochromida of the divided 

 cell within its cyst membrane a new and a smaller nucleus is formed 



t/ f 



in each of the halves. This divides by a primitive mitotic process into 

 two nuclei, one of which immediately degenerates, the shrunken 

 nucleus remaining as a highly refractive irregular mass in the cell body; 

 the other daughter nucleus then divides again, so that three nuclei lie 

 in each half of the double organism, or six altogether, two of these 

 undergoing degeneration. Two of the remaining four nuclei then 

 begin to shrink and to degenerate like the first one, until there are only 

 two functional nuclei left. After this process, which Schaudinn inter- 

 prets as equivalent to the reduction and polar body formation of 

 metazoan cells, the final encvstment takes place. The gelatinous 



