THE GENERA HERPETOMONAS AND CRITHIDIA 



235 



flagellate type (Fig. 93), arising from a distinct kinetic body, the 

 blepharoplast. The nucleus is not of the diffuse type so characteristic 

 of the bacteria and spirochetes, but is compact and cytologicaljy 

 similar to the nucleus of tissue or of typical protozoa cells, while In 

 primitive mitosis it passes through more or less complicated form 

 changes. 



All are parasites, and all are apparently typical intestinal forms of 

 definitive insect hosts. Herpetomonas is found chiefly in the stomach 



Fig. 93 



A, B, C, Herpetomonas muscEe domesticse; A, ordinary form with double flagel'um; B, 

 dividing form; C, form encysted in slime coat; D to F, Crithidia subulata Lfeger, from gut of 

 Tabanus glaucopis Meig; D, free monad form; E, gregarine-like resting forms showing with- 

 drawal of flagellum; F, the same fixed to an epitlielial cell in great numbers; k, Ivinetonucleus; 

 t, trophonucleus; d, diplosome; A to B, after Prowazek, D to F, after L^ger. X 1800. 



and intestine of various kinds of insects, H. donovani in the digestive 

 tract of the bedbug Cimex rotundatiis, while crithidia has a wide 

 range among diptera and hemlptera. With development of the blood- 

 sucking habit these various Insects have furnished the opportunity 

 for their parasites to adapt themselves to man and other intermediate 

 hosts. 



Non-flagellated, quiescent, and encysted stages are known in all 

 cases, the quiescent forms remaining passive in the digestive tract 

 (herpetomonas), or actively migrating ("gregarine" forms) to the 



