94 
Haemoflcigelicites , etc. 
tophyHits fasciatus, Ctenophthalmus agyrtes and Haematopinus spinulosus. 
It is obvious from these experiments that neither of these blood-sucking 
insects are true alternate hosts of T. lewisi, more especially as it was not 
possible to demonstrate any developmental cycle of the rat trypanosome 
in their alimentary tracts. 
It has been definitely established by J>ruce,Nabarro and Greig (1903— 
1907) that tsetse flies can only transmit certain pathogenic trypanosomes 
of Africa up to forty-eight hours after feeding on an infected animal. 
Precisely similar results have been recorded by Minchin, Gray and Tulloch 
(1906), and in addition they ascertained by actual experiments that only 
the first animal upon which the infected fly fed became infected. These 
facts prove conclusively that these trypanosomes are conveyed by tsetse 
flies in a purely direct and mechanical way (see Appendix for Bruce’s 
recent work). Minchin (1908) has however recently brought forward 
certain observations which suggest that T. gambiense undergoes some 
multiplicative changes in the alimentary tract of G. pcilpalis. After 
forty-eight hours the trypanosomes ingested by the fly are differentiated 
into two types which Minchin considers represent sexual forms; 
after ninety-six hours they however degenerate and disappear. It 
is impossible to say whether these changes represent part of the 
developmental cycle of T. gavibien.se. Koch (1906—07) also claims 
to have shown that T. brucei when ingested by G. fusca and G. tachi- 
noides undergoes a true evolutionary cycle in the alimentary tracts 
of the flies, and lastly Stuhlmann (1907) has described what he 
considers to be the development of T. brucei in G. fusca bred in captivity. 
Woodcock, remarking on the above observation, says, that there is good 
reason to suppose that for a given pathogenic trypanosome there is a 
particular insect, which is a true alternate host, and that here, as 
among leeches, there are right and wrong hosts. He concludes this 
section by drawing attention to Minchin’s (1908) recent hypothesis on 
the method of infection of trypanosomes. It will be remembered that 
this author’s view is based on the discovery of the encystment of one of 
the flagellates of G. palpalis in the proctodaeum of the fly. As the 
transmission of trypanosomes is intimately connected with their life 
cycles we shall deal fully with this subject when considering the section 
devoted to the life cycles of these parasites. 
In the section devoted to the habitat and effects of trypanosomes on 
their hosts, vertebrate and invertebrate, Woodcock first refers to 
Schaudinn’s observations on T. noct-uae in Cidex pipiens ; the extensive 
migration of the flagellates in the mosquito are quoted as an example 
