SPOROZOA, TELOSPORIDIA, COCCIDIA 269 



free in the gut lumen, make their way into new host cells and 

 repeat the process {b). Instead of growing into schizonts, 

 some merozoites transform themselves into macro- or micro- 

 gametocytes (c). Each macrogametocyte contains refractile 

 bodies, and becomes mature macrogamete, after extruding part 

 of its nuclear material {d. e). In the microgametocyte, the 

 nucleus divides several times and each division-product as- 

 sumes a compact appearance {f-h). The biflagellate comma- 

 shaped microgametes thus produced, show activity when freed 

 from the host cells {i). A microgamete and a macrogamete unite 

 to form a zygote which secretes a distinct membrane around 

 itself (j). The nucleus divides twice and produces four nuclei 

 (k-m). This stage is known as the oocyst. Each of the four 

 nuclei becomes the center of a sporoblast which secretes a 

 membrane and transforms itself into a spore (n). Its nucleus, 

 in the meantime, undergoes a division, so that two sporozoites 

 become developed in the spore (o). Thus an oocyst of this spec- 

 ies contains four spores and eight sporozoites. Oocysts in the 

 fecal matter of the host become the sources of infection in 

 new hosts. 



In dividing the suborder into the following four families, 

 Reichenow's scheme has been adopted: 



Body cylindrical or vermiform ; schizogony in motile stage 



Family 1 Selenococcidiidae 



Body not cylindrical nor vermiform 



Alternation of generations and of hosts Family 2 Aggregatidae 



No alternation of hosts 



Association of gametocytes begin early; numerous microgametes. . 



Family 3 Dobellidae 



Gametocytes independent Family 4 Eimeriidae 



Family 1 Selenococcidiidae Leger and Duboscq 



Genus Selenococcidium Leger and Duboscq. Parasitic in 

 the intestine of the lobster in Europe. The single nucleus of 

 the vermiform trophozoite divides three times, producing eight 

 nuclei. The trophozoite becomes rounded after entering the cell 

 of the gut-epithelium and divides into eight schizonts. This is 

 apparently repeated. From these develop gametocytes. Num- 

 erous microgametes are formed from a microgametocyte. Copu- 

 lation and sporogony unknown. Only one species. 



