582 ■ FAMILY: TRYPANOSOMID^ 



As regards the trypanosomes which have blood-sucking arthropods as 

 their vectors, it is not definitely known whether the development is in the 

 anterior or posterior station, though the behaviour of T. hoclii of the 

 crocodile in the tsetse fly is suggestive of a contaminative method of 

 infection. 



T. kochi Laveran and Mesnil, 1912.- — The crocodile trypanosome was 

 first seen by Minchin, Gray, and Tulloch (1906) in Uganda, but no descrip- 

 tion was given. Koch (1906) studied it in greater detail, and suggested 

 the possibility that certain flagellates (T. grayi, Herpetotnonas grayi) 

 frequently encountered in tsetse flies had their origin in the trypanosome 

 of the crocodile, on which the flies were noted to feed (see p. 373). As 

 Laveran and Mesnil (1912) have pointed out, Koch did not suppose that 

 the flagellates of the flies, which he thought might have developed from 

 the crocodile trypanosome, were in any way related to T. gambiense, 

 though writers have wrongly attributed this view to him. Kleine and 

 Taute (1911) described experiments which gave definite support to Koch's 

 view of the development of the crocodile trypanosome in tsetse flies. 

 In one experiment, thirty-two bred flies {Glossina palpalis) were fed on a 

 crocodile, with the result that eleven were found to harbour H. grayi 

 when dissected eight to fourteen days later. They believed, however, 

 that the tsetse flies could acquire the flagellates from other hosts than 

 the crocodile. Ross, P. H. (1911), found flagellates of this type in 

 G.fusca, while Bruce et al. (19146) discovered that both G. palpalis and 

 G. hrevipalpis were liable to be infected with H. grayi. They suggested 

 that the flagellates were probably derived from the crocodile, iguana, or 

 some water bird, as both these flies resemble one another in the habit of 

 living near water. Lloyd and Johnson (1924) have found the flagellate 

 in G. tacJiinoides in Nigeria. Kleine (1919a) definitely asserts that the 

 flagellate represents developmental forms of the crocodile trypanosome. 

 Roubaud (1912), basing his conclusions on a series of negative feeding 

 experiments and on the fact that Minchin (1907) had described encysted 

 stages of the flagellate in the rectum of the flies, stated that H. grayi was a 

 flagellate peculiar to the flies, and was handed on, like other purely insect 

 flagellates, from fly to fly by means of the cysts (Figs. 173 and 220). It is, 

 however, far from clear that the bodies described by Minchin were actually 

 cysts, and it is difficult to understand how tsetse flies, either in the adult 

 or larval stages, could ingest such cysts. It seems probable that Kleine's 

 view is the correct one, in which case the name of the crocodile trypano- 

 some will be T. grayi Novy, 1906, and not T. l-ochi Laveran and Mesnil, 

 1912. Lloyd and Johnson (1924) and Lloyd, Johnson, Young, and 

 Morrison (1924), however, produce evidence that the flagellates of the 

 H. grayi type in G. tachinoides may be derived from monitors {Varanus 



