S UBFA MIL Y TRICHOMONA DINM 



351 



Remarks. — -The parasite is widely distributed all over the world. 



Morphology. — -Its shape varies, but it is generally pear-shaped, 

 measuring some 11-18 microns in length if the caudal appendage is 

 included, and some i •6-4-0 microns less if this is excluded. There 

 is a large cytostome situate anteriorly. The cytoplasm contains 

 a large, roundish, oval or slightly irregular chromatic nucleus, 

 anterior to which lies two or three granules, from which the three 

 anterior flagella take their origin. No rhizoplast can be seen. The 

 margins of the cytostome are thickened, and appear to contain a 

 fourth or posteriorly directed flagellum in the inner siderophilous rim, 

 while the outer rim appears to be homologous with a parabasal. 



Life-History. — Reproduction takes place by binary fission and 

 cyst formation. The cysts are usually egg-shaped, measuring 

 7 X 5-6 microns. The cyst wall is separated from the parasite by a 

 clear space, while the cytoplasm contains a nucleus, a blepharo- 

 plastic mass, and at times the mouth margins can be seen. Division 

 forms with two nuclei have been noted. 



Pathogenicity. — ^There is a difference of opinion. Some observers 

 consider it to be non-pathogenic, while others hold that it is may 

 cause diarrhoea. 



Subfamily Trichomonadin^ Chalmers and Pekkola, 1917. 

 Definition. — Tetramitidse with an axostyle. 



Classification. — -The ten genera belonging to this subfamily may 

 be differentiated as follows : — • 



Diagnostic Table of the Trichomonadin^. 



A. Cytostome absent : — 



I. Three anterior flagella— (i) Protrichomonas Alexeieff, 

 1911. 



II. Four anterior flagella — -(2) Monocercomonas Grassi, 

 1879. 



B. Cytostome present r — ■ 



I . Without undulating membrane : — • 

 (a) Without trailing flagellum 



1. Periplast thickened in places; four anterior 



flagella — -(3) Polymastix Biitschli, 1884. 



2. Periplast not thickened; six anterior flagella 



— (4) Hexamastix Alexeieff, 191 2. 

 {b) With trailing flagellum : — 



1 . Three anterior flagella : — 



(1) Without parabasal — (5) Eutrichomastix 



Kofoid and Swezy, 1915. 



(2) With parabasal wound around the axo- 



style — -(6) Devescovina FoA, 1905. 



2. Four anterior flagella — (7) T etratrichomastix 



Mackinnon, 1914. 



