120 
Hciemoflagellates, etc. 
inocules fortuitement par ces derniers aux vertebres, au milieu sanguin 
desquels ils ont pu s’adapter.” Leger(1902) has also advanced a similar 
hypothesis, that the Crithidia and Herpetomonas of biting insects are 
perhaps but stages in the evolutionary cycle of vertebrate trypanosomes. 
Brumpt bases his hypothesis on what he considers to be the develop¬ 
ment of certain fish trypanosomes in leeches; we have fully criticised 
his researches on the evolution of these trypanosomes in leeches, and 
have clearly shown, that as he has not rigidly excluded a natural 
Gritliidia of the leeches, his work on the fish trypanosomes cannot be 
accepted as being accurate. 
Brumpt goes on to say “A un point de vue general, mes etudes sur 
revolution des Flagelles des Poissons montrent que les cultures artificielles 
des Trypanosomes sur gelose au sang representent certainement le cycle 
evolutif dans I’hSte intermediate d sang froid ( Glossines , Puces, Taons, 
etc.); elles expliquent egalement pourquoi ces cultures reussissent mieux d 
froid qua chaud.” 
This statement is wholly inaccurate, as there is no evidence to show 
that the artificial multiplication of trypanosomes on blood agar 
“certainly represents” the evolutionary cycle in a cold-blooded inter¬ 
mediate host. It has not yet been proved that certain vertebrate 
trypanosomes of Africa, T. brucei and T. gambiense, undergo any 
evolutionary changes in tsetse flies (see p. 103 and Appendix); T. lewisi 
certainly does not undergo the same multiplicative changes in fleas as 
it does in blood agar; we have ourselves investigated this question. 
There is also no evidence to show that a vertebrate trypanosome under¬ 
goes a developmental cycle in horse flies; we have recently made a 
complete study of a Crithidia in a Tabanid, and we know it has no 
connection with any trypanosome, but is a true parasite of the fly. 
Brumpt further states, “ Actuellement, je suis bien convaincu quelles 
(la mouche tsetse) sont des hotes intermediates au meme titre que 
les Hirudinees.” Here again we have shown that the tsetse flies 
cannot be considered as true intermediate hosts of pathogenic 
trypanosomes, for the simple reason that there is no evidence to show 
that these trypanosomes undergo any development in the flies; the 
so-called developmental forms are certainly natural Crithidia of the flies. 
Again there is no proof that the trypanosomes after undergoing a 
developmental cycle in the flies pass to the proboscis and are then 
inoculated into a vertebrate, when the fly sucks its blood; the same 
may be said for the flagellates of leeches. All the evidence, at present 
to hand, appears clearly to show that the pathogenic trypanosomes of 
