THE GREGARINES AND COCCIDIA 343 



take more extensive migrations, and find their way into some other 

 organ of the body, of which they are specific parasites, such as the 

 liver, fat-body of insects, genital organs, kidneys, and so forth. 

 When they have reached the cell, of whatever tissue it may be, 

 which is their destination, they penetrate as a rule into the cyto- 

 plasm, and come to rest there, but in some cases they are intra- 

 nuclear parasites. The trophozoite grows slowly at the expense 

 of the host-cell, which is at first greatly hypertrophied as a rule, 

 but is ultimately destroyed ; and when full-sized the parasite 

 enters upon the multiplicative phase as a schizoiit. After several 

 generations of schizogony, a generation of trophozoites is produced 

 ultimately, which become sexually - differentiated sporonts and 

 proceed to sporogony. 



The great power of endogenous multiplication possessed by these 

 parasites renders them often pathogenic, or even lethal, to their 

 hosts, in contrast to the usually quite harmless gregarines. As a 

 rule, however, the production of a pathological condition in the host 

 reacts on the parasite, and stimulates, apparently, the development 

 of propagative phases, which, by passing out of the host, purge it 

 of the infection. In this way the disease ; ' coccidiosis," as it is 

 termed generally may cure itself, and the host recuperates its 

 health, but without acquiring immunity against reinfection. 



As a typical coccidian life-cycle may be taken that of Coccidium 

 schubergi (Fig. 152), from the common centipede, Lithobius forficatus, 

 described by Schaudiim (99) in a classical memoir. The complete 

 life-history may be divided into eight phases, which are described 



FIG. 52 continued : 



trating the cell ; the other two cells contain parasites (p.) in different stages 

 of growth (schizonts) : n., nucleus of the host-cell ; 0, D, multiplication 

 of the nuclei of the full-grown schizont; E, the schizont has divided 

 into a number of merozoites (mz.) implanted on a mass of residual proto- 

 plasm ; the merozoites, when set free, may either penetrate into epithelial 

 cells and become schizonts again, as indicated by the long arrow, or may 

 develop into sporonts (gametocytes) ; F, epithelial cell containing two young 

 sporonts, the one male ( $ ), with fine granules, the other female ( ? ), with 

 coarse plastinoid granules in its cytoplasm : G $ , full-grown male sporont ; 

 G $ , full-grown female sporont : k. , its karyosorne : H $ , male sporont with nuclei 

 divided up ; the remains of the karyosome are seen at the centre of the body ; 

 // V , female sporont which has expelled the karyosome : k. 2 , fragments of the 

 karyosome in the host-cell ; / $ , ripe male gametes round the residual mass 

 of the body of the sporont ; / ? , female gamete ripe for fertilization, throwing 

 out on one side a cone of reception towards the male gametes ( $ ) swarming 

 round it ; J, fertilized zygote which has surrounded itself by an oocyst (ooc. ) ; 

 inside the body the female pronucleus ( ? ) has taken the form of a spindle, 

 at one pole of which is seen the chromatin of the male pronucleus ( $ *) ; 

 outside the oocyst is seen a clump of degenerating male gametes ( $ 2 ) ; K, the 

 fertilization-spindle complete, with male and female chromatin spread over 

 it ; L, synkaryon dividing ; M, the synkaryon has divided into four ; N, four 

 sporoblasts are formed, each of which has surrounded itself with a sporocyst, 

 lying in a mass of residual protoplasm (cystal residuum) ; 0, ripe oocyst 

 containing four spores, each enclosing two sporozoites and a small quantity 

 of residual protoplasm (sporal residuum). After Schaudinn (99). 



