COCCIDIIDA 75 



those of many gregarines, and brought about in a like manner 

 by the secreting at the posterior extremity of a gelatinous fila- 

 ment that stiffens rapidly. The merozoits do not gain the open 

 in the usual way, but are destined to still further infect the 

 same host by actively penetrating into other epithelial cells 

 of the affected organ ; here they continue their growth and may 

 again and again undergo schizogony. In the Infusoria the 

 repeated segmentations finally cease and are again renewed only 

 after a conjugation : this is likewise the case with the coccidia, 

 with the difference that in the latter the two uniting individuals 

 (gametes) are differently constituted one from the other, whereas 

 in the infusoria they are almost always similar. 



When the schizogony ceases, the merozoits that had penetrated 

 the epithelial cells and there grown consist of two kinds 

 of beings differently constituted ; one kind possessing a light 

 plasm (fig. 30, xii.), the other an opaque plasm richly granu- 

 lated, while both possess a vesicular nucleus with caryosoma 

 (fig. 30, XL). In order to continue their development the dark 

 individuals must copulate, and are therefore termed either female 

 gametes or, on account of their size, macrogametes . The hyaline 

 individuals, the male individuals (microgametes) necessary to con- 

 jugation, are formed in greater numbers. They are slender bodies 

 consisting chiefly of nuclear substance, which in most species bear 

 two flagella of unequal length directed backwards, and the place 

 of insertion of which varies according to the species (fig. 30, xxe.). 



While the development of the microgametes is rapicUy advanc- 

 ing a change of the nucleus occurs in the macrogametes, parts 

 of the caryosoma (nucleolus) are extruded, and the nucleus loses 

 at the same time its vesicular shape. By this time the macro- 

 gametes are capable of conjugation, and the process takes place 

 within, the host, generally, however, outside the affected and degen- 

 erated host cells. The microgametes that have now become free, 

 leaving a very large residual body, crowd around the mature 

 macrogametes, which project a small prominence (fecundating 

 protuberance) for their reception (fig. 30, xm.). As soon as a micro- 

 gamete comes into touch with this and penetrates into the plasm of 

 the macrogamete, the latter surrounds itself with a membrane 

 which prevents the intrusion of other microgametes. The nucleus 

 of the microgamete that has gained entry amalgamates with the 

 nucleus of the macrogamete, which is then capable of forming the 

 well-known spores with shells ; it is therefore called sporont (also 

 oocyst or copula). 



