THE PROTOZOA (continued) 



SECTION G. THE HAEMOFLAGELLATES AND ALLIED FORMS 1 



Order Lissoflagellata. 2 

 Sub-Order MONADINA. 



Family TIIYPANOMORPHIDAE. 

 Genus Trypanomorpka. 



Sub-Order HETEROMASTIGINA. 

 Family TRYPANOSOMATIDAE. 



Genera Trypanophis, Trypanoplasma, 

 and Trypanosoma. 



1. INTRODUCTORY. 



THE Haemoflagellates, or Trypanosomes, although possessing in 

 common a uniform type of organisation, probably do not all belong 

 to a single, well-defined group of monophyletic origin. They are 

 preferably regarded as an assemblage of forms which have sprung 

 from two quite different stocks, the resemblances exhibited being 

 due to convergence, brought about by the acquirement of similar 

 adaptations in response to their similar and highly specialised mode 

 of life. They are entirely parasitic, their characteristic habitat 

 being the blood of a Vertebrate ; and, as is well known, certain of 

 them are the cause of severe, often fatal illness. 



The Haemoflagellates possess either one or two flagella. When 

 there are two, they originate close together, at or near the anterior 

 end of the body. One is free and directed forwards; the other 

 turns back and is attached for the greater part of its length to the 

 side of the body, by means of an undulating membrane, ultimately 

 terminating in a free portion directed posteriorly. Thus a Hetero- 

 mastigine condition is found. When only one flagellum is present 



1 By H. M. Woodcock, D.Sc. (Loud.), Assistant to the University Professor of 

 Protozoology. 



2 The classification of the Flagellates here made use of differs somewhat from that 

 adopted in the account of the Mastigophora. The position of the Trypanosomes 

 according to that scheme will be seen on reference to pp. 167, 168. 



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