692 MURIEL ROBERTSON. 
begin to appear for four to six days, although the flagellum 
itself may be present for some time, apparently more than a 
day, before it becomes motile. The earliest divisions of the 
rounded 'l'rypansome, instead of following each other imme- 
diately as in '’. vittatee, are here at intervals of at least 
twenty-four hours. The early stages of development of the 
flagellum are also very slow. 
This process by which the Trypanosome rounds itself off 
and after a number of divisions produces a definite Crithidial 
flagellate, appears to me to be more widespread among 
Trypanosomes of a certain type, notably those from cold- 
blooded hosts, than it has hitherto been considered. 
Franca observed an analogous process some time ago in the 
Trypanosome of Hyla arborea, also in IT’. granulosum.! 
Brumpt describes it for this T'rypanosome also in the leech 
Hemiclepsis, and Dutton, Todd, and Tobey” have seen it in 
Trypanosoma loricatum. 
Another point of interest in the life cycle of T. vittate 
is the very marked development of a uniform slender type of 
parasite at the end of digestion. In 'l’. raiz this also occurs, 
though here some rounded forms seem often to persist. A 
somewhat similar development occurs in T. grayi,®> where 
the last stage of the infection shows, however, two slender 
forms, one of which, a Herpetomonas-form, encysts in the 
proctodeeum of the Glossina, while the other does not encyst, 
and seems probably to be destined to transmit the infection 
by inoculation into a vertebrate host. 
I need not emphasise the absence of evidence of conjuga- 
tion. ‘This process if it occurs seems particularly difficult to 
observe in 'I'rypanosomes, and no quite satisfactory account 
of it has yet been given for this group of flagellates. 
It is a point of only shght interest, but it is curious to note 
to what an extent the infection is capable of persisting in 
1 «Bull. Soc. Portug. Se. Nat.,’ vol. i, p. 3, Dec., 1907. 
2 *Ann. Trop. Med. and Parasit.,’ vol. i, No. 3, 1907. (I have not seen 
the original memoir.) 
3 Minchin, loe. cit. 
