THE GENERA HERPETOMONAS AND CRITHIDIA 235 



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

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

 of the bacteria and spirochetes, but is compact and cytologically 

 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 muscffi domesticse; A, ordinary form with double flagellum; B, 

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

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

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

 t, troi)honucleus; d, diplosome; A to B, after Prowazek, D to F, after Lfcger. X 1800. 



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

 tract of the l)cdbug Ciincx roiundaius, while crithidia has a wide 

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

 sucking habit these various in.sects 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 



