132 



MORPHOLOGY AND CULTURE OF MICROORGANISMS 



species are parasitic, but some of these caUse very serious diseases 

 (page 824). 



The Herpeiomonad is an elongated organism which possesses tropho- 

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

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

 Crithidia is an organism very much resembling an Herpetomonas,vnth. a 

 pear-shaped body, and, sometimes, a rudimentary undulating membrane, 

 Trypanosoma is an elongated parasite which has a trophonucleus, 

 a kinetonucleus usually situated near its aflagellar extremity and an 



Fig. 9S- — -^i Trypanosoma tinea of the tench; note the very broad and undulat- 

 ing membrane in this species; B., C, T. perca 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 Herpeiomonas, 

 Crithidia and Trypanosoma are frequently found in the intestines of 

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

 site in the intestine of the house fly. The genus Try panoplasma in- 

 cludes organisms which have a flagellum at either end, as well as an 

 undulating membrane. They are parasitic in the blood of fishes. The 

 genera Cercomonas, Monas, and Plagiomonas include small, unimpor- 



