TETRASPOROCYSTIDM 



473 



Some merozoites now become differentiated into micro- and macro-ga- 

 metocytes. The former consist of finely granular cytoplasm, with little 

 reserve material, while the latter are bean-shaped and have much food- 

 material. The microgametocyte forms the microgametes by its nucleus 

 becoming irregular, and forming fine achromatic paths through the cytoplasm 

 to the periphery of the parasite, along which chromidia travel from the nucleus. 



At first, scattered evenly along the periphery, these chromidia gather into 

 patches, and finally fuse into masses, enclosing in each a vacuole. The 

 masses of chromatin lengthen, and by bending project from the cytoplasm, 

 which now forms two flagella, whose active movements set free the micro- 

 gamete. 



In the meanwhile the macrogametocyte becomes a macrogamete by expul- 

 sion of the karyosome of the nucleus. 



Micro- and macro-gametes now fuse and form a zygote with a synkaryon. 

 The oocyst, as it may be called, now passes out of the body of the host, and 

 divides into four sporoblasts. Each sporoblast now develops two vacuoles 

 and a cyst-wall, the sporocyst, so that the sporoblast is often called the spore. 

 The nucleus of the spore divides into two, while the two vacuoles fuse and the 

 cytoplasm divides, forming two sporozoites which are capable of infecting a 

 new host, being set free by the acid of the digestive juices. ( 



Sporogony takes about two to three days for completion. 



It may be as well at the present time, when so much disputation is taking 

 place re Schaudinn's work on trypanosomes, to mention that he worked out 

 this life-history, which has never been refuted, though the parasite was found 

 in company with C. lacazei Labbe and Adelea ovata H. Schneider. 



Classification of the Coccidiidea. — The usual classification is that by Leger in 

 1900, and is based upon the number of sporozoites in each cyst. 



Family i. Asporocystid^. — Sporozoites naked, no sporocysts inside the 

 oocyst. 



Family 2. Djsporocystid^.. — Oocyst has two spores. 

 Family 3. Tetrasporocystid^. — Oocyst has four spores. 

 Family 4. Polysporocystid^.— -Ooc^rst has many spores. 



Family Asporocystid^ Leger, 1900. 



The genus included in this family is Eimeriella Stiles, 1902, of which there 

 is only one species. Eimeriella nova Schneider, 1 8 19 in the Malpighian tubules 

 of Glomeris. 



Family Disporocystid^ Leger, 1900. 



The genera of this family are: Cyclospora A. Schneider, 1881 (spores dizoic) ; 

 Diplospora'LdJobQ, 1893 (spores tetrazoic) ; Isospora A. Schneider, 1881 (spores 

 polyzoic) . 



Isospora A. Schneider, 1881. 

 Definition, — Disporocystidse with polyzoic spores. 



Isospora bigemina Stiles, 1 89 1. 



Synonym. — Cytospermium villorum intestinalium canis et felis Rivolta, 1874. 



This parasite lives in the intestinal villi of dogs and cats, and is distinguished 

 because it is small and because it is in pairs, the oocyst dividing into two equal 

 portions, which become encysted and form two spores [vide Coccidiosis in 

 man infra). 



Family Tetrasporocystid^ Leger, 1900. 



Type Genus. — Eimeria A. Schneider, 1874. 



Synonym. — Coccidium Leuckart, 1879 (the dizoic spores are spherical or 

 oval). Other Genus: Crystallospora Labbe, 1896 (the dizoic spores have the 

 form of a double pyramid) . 



