1911.] Parasitic in Pediculus vestimenti. 



507 



Occurrence of the Parasites in the Host. 



Herpetomonas pediculi exhibits three typical stages in its life-history — 

 the pre-flagellate, flagellate, and post-flagellate stages. So far the examina- 

 tion of the mouth parts of the lice has shown no parasites. The pre-flagellate 

 stage of the parasite occurs chiefly in the oesophagus and proventriculus of 

 the adult louse, and throughout the alimentary canal of the immature 

 insect or larva. The flagellate stage is found at its best in the mid-gut 

 of the mature louse, while the extreme intestinal and rectal portions of 

 the gut contain the post-flagellates. The latter are also found in the 

 excrement. The late larva may contain a few flagellate parasites. 



Detailed examination was made of the reproductive organs and ova of 

 the lice, but no parasites were found therein. The possibility of the 

 hereditary infection of the lice with H. pediculi was, in my opinion, excluded 

 so far as the specimens that I examined were concerned. The parasites have 

 not been found in organs other than those of the alimentary tract. The 

 diverticula of the alimentary canal apparently are uninfected. 



Movements. 



Movements of H. pediculi are most easily observed in the fully developed 

 flagellate stage. They are also very vigorous during division, but as the 

 object of the said movements then is to complete the fission of the organism, 

 they are of a somewhat exceptional character. 



Usually movement is brought about by waves of contraction followed by 

 relaxations passing down the body, while progression is aided by the lashing 

 of the flagellum, which is forwardly directed. The type of movement is 

 somewhat euglenoid, and the occasional concentration of the cytoplasm into 

 the anterior end produces a " peg-top " effect that is very characteristic. 

 The progression is somewhat spasmodic, consisting of alternate slow move- 

 ments and rapid darts forward, accompanied by a slight rolling from side 

 to side. Keversal of the direction of motion is easily accomplished. The 

 organism either swings as a whole in a semicircle, the posterior end acting 

 as a centre of rotation, or the flagellum bends back parallel to the body, 

 which then swings suddenly in a semicircle, and so comes to lie in a straight 

 line with the flagellum, after which the parasite moves away in the opposite 

 direction from what it was traversing previously. 



The flagellum often lashes vigorously, and when obstacles are encountered 

 appears to test them by touching them rapidly in different spots. 



Rotatory movements occur when the Herpetomonas becomes fixed to debris 

 in the lumen of the gut. The organism lashes its flagellum violently, and 



