ISOSPORA. 169 



a thick chitinous wall after it has passed into the lumen of the 

 intestine. Oocysts containing two sporoblasts may be found 

 in the gut, and in this condition are passed out in the faeces. 

 Outside the body the sporoblasts in the oocyst elongate, acquire 

 a double contour, and become sporocysts. In each sporocyst 

 are developed four club-shaped sporozoites and a large rounded, 

 granular, residual body. 



Dimensions. — Oocysts, egg-shaped type 35-45^ by 25-35 )u. 

 (39-48 |U by 26-37 ^u, according to Wenyon), rounded type 

 25-37 /i by 21-37 ^u,; microgamete 3-1 ft; sporocysts 18-4/x 

 by 11-4^. 



Remarks. — ^Knowles (1928) stated that Isospora infection 

 was not micommon in cats in Calcutta, and that infection 

 was absolutely hmited to the epitheHal cells, but did not mention 

 the name of the species or give the dimensions of the oocysts. 

 On my request for further information, Knowles and Das- 

 Gupta (1934) examined the stools of 13 cats and 8 kittens, 

 and by the employment of concentration method found 

 14 out of 21 animals examined to be infected. In all they 

 measured 353 oocysts. After discussing the views of Wenyon 

 and of Dobell they are of opinion that the evidence collected 

 by them seems to point to two " types " being present, 

 though they are not in a position to assert that they are 

 different species. The smaller, oval type of oocyst encountered 

 measured from 20-4 ju, by 15-3 ju, to 47-6//, by 40-8 ju,, and the 

 larger, egg-shaped type of oocysts measure 38-45 [x by 

 27-36 /x. 



Their " type A" or small oocysts are always perfectly oval 

 and resemble /. rivolta, and the " tj^^pe B " or large oocysts 

 are more egg-shaped, pyriform or ovoid, and resemble I. felis. 

 I am inchned to think that the form of the oocyst and the 

 measurements given show that the two " types " are distinct 

 species, as is held by Wenyon and Reichenow. 



The vast majority of the oocysts seen by Knowles and Das- 

 Gupta in freshly passed faeces were in the unsegmented state, 

 with the protoplasmic contents present as a single spherical 

 mass within the thick oocyst waU, while in a few the first 

 nuclear division had taken place and two sporoblasts were 

 forming, although the sporocysts had not yet formed. They 

 also noted the occurrence of a fair number of motile sporozoites 

 in the contents of the jejunum and ileum, both in the fresh 

 preparations and in fixed and stained films, from which 

 they conclude that an occasional oocyst may develop to maturity 

 within the lumen of the gut, although the vast majority are 

 passed in the unsegmented state. 



Habitat. — ^Epithelial cells of the small intestine of cat, 

 Felis domesticus Linn. : Bengal, Calcutta. 



