338 



THE PROTOZOA 



reproduce their like for many generations, but which finally produce mero- 

 zoites which grow tip into paucinucleate schizonts, and these produce mero- 

 zoites which grow up into sporonts. The sporogony of this genus is also 

 peculiar. Two sporonts associate, and the nucleus of each sporont divides 

 into three ; the body of each sporont then divides into a smaller cell with one 

 nucleus and a larger cell with two nuclei ; the small cell is a gamete, which is 



FIG. 149. General diagram of the life-cycle of Schizocystis gregarionides, after 

 Leger (617, ii.)- A, Sporozoite escaping from the spore ; B, C, D, E, growth 

 of the sporozoite into the multinucleate schizont, of which there are two 

 types: the vermiform schizont (a), which attaches itself to the epithelium by 

 its anterior end, and the massive schizont (6), which lies free in the gut of the 

 host ; F, division of the schizont into a number of merozoites, which may 

 either grow into schizonts again (Q 1 , G 2 ), or may grow into sporonts (C? 3 ) ; 

 H, young sporonts ; /, association of two full-grown sporonts ; J, formation of a 

 common cyst by two associated sporonts ; K, division of the nuclei in the 

 sporonts ; L, formation of the gametes by the sporonts ; M , copulation of the 

 gametes ; N, each zygote becomes a sporoblast and forms a spore. 



enveloped by the larger binucleate cell. The two gametes copulate, and 

 the zygote becomes a single spore with the usual eight sporozoites ; the two 

 binucleate envelope- cells form a protective envelope to the spore during its 

 development, and die off when it is ripe (L6ger, 617, i.). 

 (For Schaudinnella see p. 355.) 



