184 E. A. MINCHIN. 
persist, there are many possibilities which suggest themselves. 
First, they might pass into some other organs of the fly; 
against this I may urge that I have repeatedly examined all 
organs of the fly likely to harbour trypanosomes at, various 
periods after infection, and never found a trypanosome or 
anything that suggested a stage of a trypanosome, outside 
the digestive tract. Secondly, they might assume, some 
minute ultra-microscopic form; in that case, however, the 
function in the life-cycle of such a form would almost 
certainly be that of infecting a new vertebrate host by inocu- 
lation, and every experiment to produce infection with 
Glossina palpalis more than forty-eight hours after the 
fly had infected itself gave negative results. A third. possi- 
bility is suggested to me by my observations on the encysta- 
tion of T. grayi; it is possible that the trypanosomes which 
disappeared from the stomach and intestine passed on into 
the proctodeum in order to become encysted there. Itisa 
matter of the deepest regret to me that I did not make smears 
of the proctodzeum, but the idea of such a possible develop- 
ment of the trypanosomes was not present in my mind when 
I was in Entebbe; since I never saw T. gambiense in the 
proctodeeum, I did not make any preparations of this region, 
and so the golden opportunity of deciding this point was lost 
to me. 
Dutton, Todd, and Hannington (15) have published obser- 
vations on the fate of ‘I’. gambiense after being taken up 
by various Arthropods. In G. palpalis they find “ unaltered 
parasites in the alimentary canal up to forty-eight hours ; 
living but altered trypanosomes up to seventy-two hours after 
feeding.” This does not agree with my experience ; I find 
the trypanosomes beginning to alter in character a few hours 
after feeding; by alteration, however, the authors mean, 
apparently, coarse or violent modification of trypanosome- 
structure. In Stomoxys trypanosomes were found up to 
twenty hoursafter feeding. Inthe larvaof Au chmeromyia 
luteola they were found up to twelve hours after feeding ; 
in Anopheles up to forty-two hours. Trypanosomes were 
