COCCIDIUM CUNICULI 



763 



biliary passages. On coming in contact with an epithelial cell the sporozoiite by its 

 pointed anterior end penetrates and passes entirely into the cell, reaches the centre 

 of the cell-protoplasm (between the nucleus and the free surface), loses its motility 

 and soon assumes a new appearance, the schizont (fig. 364), which grows at the 

 expense of the cell in which it is living and multiplies by asexual division (schizogony). 



III. In the body of the host. 



A. Schizogony (Asexual reproduction). The schizont, which has no enveloping 

 membrane, grows and assumes a spherical form, while its protoplasm becomes 

 hollowed out by large alveoli filled with a clear fluid. The nucleus soon divides into 

 a large number of daughter nuclei which pass towards the periphery : the proto- 

 plasm divides into an equal number of segments and accumulates around the nuclei. 

 Thus a number of claviform corpuscles are formed, arranged at first like the quarters 

 of an orange but later becoming free and exhibiting movements similar to those of 

 sporozoa. These represent the merozoites (fig. 365). 



FIG. 365. Cocddium cuniculi. 

 nucleus ; 

 Simond.) 



Schizogony. A, multiplication 

 B, multiplication of the cell ; C, fully-grown merozoites. 



of the 

 (After 



At this moment the epithelial cell bursts and the merozoites are set free : some 

 die in the intestine of the rabbit ; others penetrate fresh epithelial cells, where 

 one of two things may happen. 



In some cases a merozoite entering a healthy cell loses its motility, becomes 

 spherical, increases in size and forms a true schizont and at once begins to multiply 

 in the manner already/ described. By repeated schizogony the parasite can multiply 

 very quickly in the rabbit's tissues and this explains the very rapid manner in which 

 infection sometimes spreads through the body. 



In other cases a merozoite, after penetrating an epithelial cell, undergoes changes 

 preparatory to a sexual mode of reproduction. 



B. Sporogony (Sexual reproduction). In this case some of the merozoites after 

 entering a cell of the host are converted into female cells, macrogametes, others into 

 male cells, microgametes. 



1. Macrogametes. The merozoite destined to become a macrogamete slowly 

 increases in size, and provides itself with reserve material in the form of chromatin 

 granules. The nucleus contains a karyosome which before long is expelled, and 

 the macrogamete, elliptical in shape, exhibits contractile movements which generally 

 result in its passing out of the cell-host ; it then remains on the surface of the epi- 

 thelium where it can be easily reached by the microgametes. The now mature 

 macrogamete is spherical, non-motile, and has a sharply defined nucleus ; the granu- 

 lations pass to the periphery, fuse, and form an enveloping membrane pierced at 

 one end by an orifice, the micropyle. 



2. Microgametes. The merozoite about to be transformed into a male cell has 

 no enveloping membrane or granules of reserve material. It grows rapidly and 

 soon becomes converted into the microgametoblast from which the microgametes will 

 take origin. The nucleus, which has a large karyosome, divides into a number of 

 daughter nuclei and these range themselves round the periphery of the organism 

 and around each of them a mass of hyaline protoplasm collects. The daughter 

 nuclei soon become flattened, elongated and comma-shaped. These are the micro- 

 gametes ; they continue to elongate and iwoflagella appear at their anterior extremity 

 (the point of insertion of the flagella varying in different species) : the- microgametes 

 are motile and, becoming free, leave the microgametoblast, which forms a residual 

 body and is soon destroyed. 



