5 8 SOME MINUTE ANIMAL PARASITES 



The life-history of the Herpetomonas of the louse 

 has a peculiarly human interest, and it is the most 

 recently described organism of its class. Also, 

 although lice suck the blood of man, the Herpeto- 

 monas they contain has no effect, either on human 



beings or on com- 

 mon animals, as 

 has been shown 

 by numerous ex- 

 perimentsextend- 

 ing over three 

 years. 



The earliest 

 known herpeto- 

 monad was the 

 one occurring in 

 the common 

 house-fly, the 

 flagellate being 

 Herpetomonas 

 musccs domesticcz. 

 Another flagel- 

 late, H . culicis, is 

 present in the 

 common gnat, 

 and has the dis- 

 tinction of being 

 the first Herpeto- 

 monas whose life-cycle was worked out, this being 

 accomplished by Captain Patton, I. M.S., who also 

 detailed the life-history of H. lygcei (a form occurring 

 in the plant-bug, Lygceus militaris), and of several other 



F. 



FIG. 15 HERPETOMONAS PEDICULI : POST- 

 FLAGELLATE STAGES 



A-E show the progressive shortening and 

 absorption of the flagellum and the con- 

 traction and rounding of the body ; F 

 shows encysted form (post-flagellate), 

 surrounded by a thin, varnish-like cyst 

 wall 



