202 EH. A. MINCHIN. 
partner has a long free flagellum, the other a short one. I 
am inclined to identify the two varieties of the ordinary form, 
termed above the serpentine and the vermiform types, as 
male and female respectively, and fig. 143 supports this view ; 
but it must be confessed the evidence is meagre. Some of 
the large ordinary forms (figs. 188, 139) might then be really 
zy gotes. 
A few words, in conclusion, upon the differences between 
T. grayiand '’. gambiense and the nature of the former. 
As a rule the two forms: can be distinguished at a glance, 
whether in the living condition or in preparations. ‘T. 
gambiense is sluggish in its movements, and when observed 
in vitro seldom moves out of the field. T. grayi, on the 
contrary, moves with great rapidity, and is very difficult to 
keep in the field. The slender forms, in particular, dart 
across like arrows. Butin two flies containing 'T. gambiense 
seventy-two hours after,infection, I observed that the trypano- 
somes were very active in their movements (Oct. 22nd, p. 237), 
and in the preparations very large trypanosomes were found. 
The most constant distinctive feature of IT’. gray is its 
large rod-shaped kinetonucleus. In T’. gambiense 7 may be 
round or rod-shaped, but is always much smaller than in 
T.grayi. Moreover, in T’. grayi, though the position of 7m is 
variable, it is most usually at the side of, or in front of, N,. 
and when division is about to take place, 1 is always in front 
of N. In T. gambiense, so far as I have observed, n is 
always behind N by at least half the distance between N and 
the posterior end of the body. It is sometimes difficuit to 
draw clear distinctions in words, but I think the figures show 
that it is impossible to confound T. grayiand T. gambiense 
at any stage. It is, nevertheless, interesting to note that in 
the two instances in which T. gambiense did not show any 
signs of degeneration on the third day in the fly, it made 
some approach to ‘I’. grayi in its appearance and activities. 
T. grayi, as seen in the fly, is probably a good deal different 
from the same species in the blood of the vertebrate host. . 
J think there can be no doubt that the forms described by 
