STUDIES ON CEYLON HAMATOZOA. 683 
The question of the surviving of the Trypanosome in the 
leech has to be considered. It is a matter which is not easy 
to settle quite definitely, but I do not think that it occurs in 
this case. Leeches from uninfected hosts showed no para- 
sites. I had a tortoise with only Heemogregarines in its 
blood, and I never got Trypanosomes in leeches from this 
individual. As far as my observation goes (both as regards 
the investigation of the live creature and of sections) the 
parasite is never found outside the alimentary tract, and, 
while to be found in the intestine, is much more a crop 
parasite than, for instance, ‘Tl’. raiz in Pontobdella. 
How exactly the infection is transmitted to the tortoise in 
the act of sucking I do not know. But this much is pretty 
clear, the leech seems to suck by rhythmic contractions, that 
is to say, the suction is periodically inhibited. 
{ do not know if the Trypanosome, which is certainly 
slightly rheotropic, is sufficiently so to swim against the 
inward flow of blood during the suction time, but it might 
conceivably be able to do so in the intervals during which 
this is suspended. Further, the skin of the host must be 
pierced before suction begins, and it may be during this part 
of the process that the parasites are communicated to the 
vertebrate. 
The habits of the Glossiphonia seem admirably adapted to 
the requirements of an intermediate host : its trick of wander- 
ing from one tortoise to another, its apparent conservatism in 
the choice of a host, and the relatively rapid digestion are all 
features favourable to the spreading of such a parasite as a 
‘Trypanosome.! 
II]. Opservations ON STAINED MATERIAL. 
So much then for the observations upon the live material. 
The material for staining was treated in various ways; films 
were made and dried in air, then fixed in absolute aleohol— 
or they were exposed to osmic vapour and then allowed to 
' See note on p. 693. 
