TRYPANOSOMES IN TSETSE-FLIES AND OTHER DIPTERA. 185 
also obtained in a louse. There is nothing that calls for 
notice in their observations except the ‘‘ rounded forms,” 
which they believe to “ arise from the englobation of single 
trypanosomes which have cast off blepharoplast and undulat- 
ing membrane and become spherical.” ‘The authors describe 
their formation more in detail in the rat flea (louse ?), in 
which they note “ granular, indistinct, obviously degenerating 
parasites.” I regard the rounded form seen by Dutton, 
Todd, and Hannington as trypanosomes succumbing to, and 
being digested by, the digestive juices of the alimentary 
canal, and quite distinct from the rounded forms described 
by Koch (20) and Stuhlmann (41), which probably form part 
of a true developmental cycle. JI have not found rounded 
forms of T’. gambiense in any of my preparations. 
III. OpseRVATIONS UPON TRYPANOSOMA GRAYI. 
My material of this trypanosome is limited, because, for 
reasons explained above, I did not systematically search for it 
in Glossina palpalis, so that all the instances of its occur- 
rence that came under my ken were in flies used by me for 
studying the changes undergone by ‘I’. gambiense. In this 
way I found inall six flies containing I’. grayi. Fortunately 
this trypanosome, when it occurs at all, is found in such vast 
swarms that a single infected fly furnishes an. abundant 
material. Hence, I have been able to discover some facts of 
interest relating to this form, notably the process of encysta- 
tion, not previously observed, so far as I am aware, in any 
trypanosome, and I have also studied carefully the distribution 
- and occurrence of the many forms of this trypanosome in the 
different regions of the intestine of the fly; but with regard 
to this latter point, it is to be regretted that my material is 
defective, inasmuch as none of my five flies had any 
trypanosomes in the proventriculus, so that I have had no 
opportunity of studying the forms occurring in this part of 
the digestive tract. In spite of much searching I have never 
found this trypanosome in any organs of the fly other than 
