216 E. A. MINCHIN. 
not a suitable host! for the development of IT. gambiense, 
though efficientin transmitting this trypanosome mechanically, 
while in other species of tsetses T. gambiense is capable of 
passing through a developmental cycle? ‘To find support for 
this conclusion it is not necessary to rely solely on the analogy 
of the well-known facts of the transmission of malaria and 
inosquitoes. ‘The interesting studies of Brumpt (9, 10, 11) 
on the transmission of fish-trypanosomes by leeches have shown 
that for a given species of trypanosome there is what may be 
termed a right leech, and that other species of leeches are wrong 
ones. Thus, for T. granulosum of the eel the right leech, 
according to Brumpt,is a Hemiclepsis, in which the develop- _ 
ment is completed, while three others, namely, Calobdella 
punctata, Hirudo troctina, and Piscicola geometra, 
were wrong leeches, in which only a part of the development 
was passed through. ‘There is no reason to suppose that in 
the case of trypanosomes the same intimate relation between 
host and parasite does not obtain that is known to occur in 
the case of other parasites, protozoan or metazoan. 
Still less can I adhere to the peculiar view of Novy, 
that trypanosomes do not go through any life-cycle in 
their invertebrate hosts, but only a process of multiplica- 
tion analogous to that seen in artificial cultures. Novy 
seems to regard the invertebrate host as nothing more, so 
far as trypanosomes are concerned, than a kind of flying 
culture-tube, an imitation of art by Nature; and, lke some 
1 From the experiments of Bouet (2) and Roubaud (89) there is evidence 
for regarding G. palpalis as the true host for T. dimorphon. 
2 In his most recent report Koch (22) states that in ‘“ Glossinen ” 
(presumably G. palpalis) several species of trypanosomes can be found; one 
of which, so far found five times, can be identified with T. gambiense. It 
is not stated, however, in what way its identity is established ; to judge from 
Koch’s report, which is far from explicit, the identification was made on 
morphological grounds, a very unsafe criterion. Koch further states that in 
two of his five cases the trypanosomes were found in the salivary glands— 
a state of things contrary to all previous recorded experience (compare 
Stuhlmann [41], p. 23); without further explanation of these statements, further 
comment is impossible. 
