198 E. A. MINCHIN. 
the germination of the cyst, and that I have not been able 
to do. . 
In a few rare cases I have observed division within the cyst ; 
one such case is figured (fig. 2083). 
Having, in the foregoing, described the various forms 
under which I have met with Trypanosoma grayi in 
Glossina palpalis, I propose now to discuss the significance 
of the different forms and their relations to one another. This 
is not an easy matter in the incomplete state of our know- 
ledge of the life-cycle of this trypanosome. Moreover, the 
forms which T. grayi assumes are so different that they 
might well be taken for different species were it not that 
they are all linked by transitions. Taking first the forms 
which I have grouped together as the “ ordinary” type, we 
may, I think, regard them as the multiplicative form of the 
trypanosome in the fly, that is to say, the form which, when 
taken from the vertebrate host, has the function of feeding, 
growing, and multiplying by division to produce the vast 
swarms of trypanosomes which are found in infected flies. I 
base this opinion on the following grounds: First, the large 
size which this form reaches, a character not likely to be 
exhibited by forms destined to pass back from the fly to a 
vertebrate host; such forms are more likely to be of small . 
size ; secondly, the frequent occurrence of division and pro- 
duction of young and intermediate forms; thirdly, the great 
variability of this form, especially in the position of the kineto- 
nucleus. ar from being constantly in front of the nucleus, 
the kinetonucleus may be behind it or even terminal. From 
our knowledge of other trypanosomes, I think we may 
assume that the forms with » terminal probably represent 
most nearly the form under which T. grayi ‘occurs in the 
vertebrate host. It is true that it is not even known that 
this trypanosome has a vertebrate host. I have elsewhere 
(P. R. S., 8 79, p. 38) brought forward arguments to favour the 
belief that T. grayi has a vertebrate host, and is not simply 
a parasite of tsetse-flies, and in my opinion the occurrence of 
