GENERA: LEPTOMONAS, CRITHIDIA, HERPETOMONAS 369 



already pointed out, H. muscarum, like the flagellates considered above, 

 passes from insect to insect in cysts voided in the fseces by infected 

 individuals. It differs from L. ctenocephali and C. gerridis in that the 

 flagellate may assume the trypanosome form in the course of its develop- 

 mental cycle. 



Patton (1921) records the successful culture of H. muscarum in N.N.N. 

 medium. The strain was obtained by dissecting out the peritrophic 

 membrane of a Lucilia argyricephala, and inoculating the medium with 

 some of the contained flagellates. Glaser (1922), who also succeeded in 

 cultivating the organism, has shown that grasshoppers can be infected by 

 inoculation into the body cavity. The cultures obtained by Drbohlav 

 have been noted above (p. 3G4). 



Franchini and Mantovani (1915), and Fantham (1922), claim to have 

 infected rats and mice with H. ynuscarum. Glaser (1922) and Becker 

 (1923a) have been unable to confirm this observation. 



OTHER MEMBERS OF THE GENERA LEPTOMONAS, CRITHIDIA, 

 HERPETOMONAS. 



As will be seen from the list (p. 14:02), the number of invertebrate 

 flagellates is very great, but in the majority of cases nothing like a com- 

 plete cycle has been observed. In some of those where it is known, as, 

 for example, L. ctenocephali, L. culicis, L. jaculum, C. pulicis, C. gerridis, 

 etc., the cycle of development is a comparatively simple one, the encysted 

 forms ingested growing through the pre-flagellate form into the adult 

 flagellate, and then retrogressing through a post-flagellate form into the 

 cyst, which escapes in the faeces and is ingested by a new host. In most 

 cases the feeding habits of the adults, as the house fly, are such that 

 infection by the ingestion of cysts is possible. In other cases, as, for 

 instance, fleas and sand flies, the adults are blood feeders, which have 

 no opportunity of ingesting cysts. There are, however, larval stages, 

 which are omnivorous feeders, and the adults become infected during 

 metamorphosis from the infected larvae. Other blood suckers have no 

 stage capable of ingesting cysts, and it would appear that infection can 

 be derived only from the blood. The crithidial infection of Hyalomma 

 cegyptium, mentioned above, is of this type. The recent discovery of a 

 Leptomonas in the proboscis and intestine of Glossina morsitanshy Lloyd 

 (1924) afiords another instance of the same type. The origin of this Lepto- 

 monas is not known, but if it conforms with other flagellates of tsetse flies, 

 it must have originated from the blood of some vertebrate. It may be 

 connected with the leishmania infections of man which occur in Nigeria, or 

 be derived from the blood of a reptile on which these flies readily feed. 



I. 24 



