SUBFAMILY HERPETOMONINM 



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These five genera may be differentiated as follows :• — 



{a) Undulating membrane absent : — 



Genera : Herpetomonas, Leptomonas, Leishmania, Hcemo- 

 cystozodn. (Probably all belong to one and the same 

 genus, Herpetomonas.) 

 {b) Rudimentary undulating membrane present. —Genus 

 Crithidia. 



Morphology. — The flagellate stage of the Herpetomoninse is 

 usually an elongated spindle-shaped mass of cytoplasm composed 

 of an inner granular endoplasm surrounded by a periplast (ecto- 

 plasm). In the cytoplasm lies a chromatinic mass, the tropho- 

 nucleus, which, when properly treated, appears to be of the nature 

 of a protokaryon. On the flagellar side of this lies another mass of 

 chromatin called the kinetonucleus, and further back on the same 

 side a minute bead— the blepharoplast — from which the fiagellum 



Fig. 80. — -The Life-History of a Herpetomonas. (After Fantham.) 



passes through the cytoplasm, either directly, and so forming no 

 undulating membrane and becoming a free flagellum, or it carries 

 the cytoplasm with it, forming a rudimentary undulating membrane. 



Life-History. — The flagellate forms are usually the inhabitants 

 of the intestine of the arthropoda, but some live in plants. 



They can multiply in their arthropodal host by longitudinal 

 division of the flagellate stage, but this may become rounded binu- 

 cleate cysts, which, passing from one host with the faeces, can infect 

 a new host. 



In the new host it appears as a non-flagellate binucleate rounded 

 form, often called a Leishmania-like body, or the Leishmaniform 

 stage, which develops in due course into the flagellate stage again. 



Thus in the life-cycle there are the following stages : — • 



1. The flagellate stage. 



2. The post-flagellate or encysted stage. 



3. The Leishmaniform stage. 

 ^ 4. The flagellate stage again. 



