PROTOZOA 



135 



A Herpetomonas is an elongated organism which possesses trophonu- 

 cleus and kinetonucleus. The latter is situated near the flagellar or 

 anterior end of the parasite, and from it arises a terminal flagellum. 

 A Herpetomonas has no undulating membrane. A Crithidia is an organ- 

 ism like a Herpetomonas, but possessing an undulating membrane. 

 A Trypanosoma is an elongated parasite which has a trophonucleus, 

 a kinetonucleus usually situated near its aflagellar extremity and an 



FIG. 96. A, Trypanosoma tinea of the tench;* note the very broad and undulat- 

 ing membrane in this species; B., C., T. percce of the perch, slender and stout forms. 

 (After Minchin, X 2000.) 



undulating membrane along the border of which the flagellum extends 

 to terminate in a whip-like appendage. Species of Herpetomonas, 

 Crithidia and Trypanosoma are frequently found in the intestines of 

 insects. One species of Herpetomonas is a frequent and harmless para- 

 site in the intestine of the house fly. Many serious diseases are caused 

 by trypanosomes. The genus Try pano plasma includes organisms 

 which have a flagellum at either end, as well as an undulating mem- 

 brane. They are parasitic in the blood of fishes. The genera Cerco- 

 monas, Manas, and Plagiomonas include small, unimportant flagellate 



