224, E. A. MINCHIN. 
tive and unpractical. Phylogenetic speculations may, how- 
ever, have a practical value, if only in widening our point 
of view, and at the same time formulating the possibilities 
of development, for which the investigator should be prepared. 
I think the studies of trypanosome development have been 
too much dominated by preconceived assumptions, and that 
investigators have too often been biassed by analogies and 
predisposed to force new facts into old formule. It is not 
necessary to suppose that the development of trypanosomes 
should be in all cases of the same pattern. If it be true that 
amonest trypanosomes two quite distinct lines of evolution 
are comprised, we may expect to find the greatest differences 
in their mode of development. . 
In conclusion, I may say that with regard to the main 
problem of my investigations, namely, the life-cycle of T. 
gambiense, it is a matter of great regret to me that I have 
little but negative results to bring forward, and can only 
offer speculations and hypotheses where I had hoped to have 
contributed definitely established facts. It was my desire to 
return to my investigations on this subject, but owing to the 
lack of the necessary support I have been obliged to abandon 
the idea. I think now, however, for reasons given above, it 
would be better to study the etiology of sleeping sickness in 
regions where it is endemic and where other species of 
tsetses besides G. palpalis occur. In both these respects 
Uganda is probably less suitable for the study of the 
problem than the Congo. 
The following propositions summarise briefly the conclusions 
or personal opinions to which my investigations or reflections 
have led me. 
(1) In Uganda Trypanosoma gambiense begins, but 
does not complete, a developmental cycle. in Glossina 
palpalis, the method of transmission by this ilps in this region 
being purely mechanical and direct. 
(2) In other Diptera also, Tl. gambiense starts on a 
development in a precisely similar manner, but without getting 
so far, or persisting so long, as in Glossina palpalis. 
