STUDIES ON CEYLON HAIMATOZOA. 691 
followed very clearly in different infections. Thus Pl. 17, 
figs. 31—33, came from a quite empty leech, and only this 
type with very slight variations was present. PI. 17, figs. 18 
—27, come from a leech in the middle period of digestion, 
and this final type is just beginning to appear in isolated 
specimens. In another leech a little further advanced it is 
more numerous than any other, but not exclusively in pos- 
session of the field. 
I have never seen division in this type which appears at 
the end of digestion. J am inclined to think, although there 
is no actual evidence, that these forms die off unless in- 
jected into the blood of the vertebrate.! 
Exactly what happens to the forms which disappear during 
the course of digestion is not very clear. ‘The broad forms, 
however, appear to give rise to such forms as Pl. 17, figs. 
29—33, simply by division and direct development. ‘The 
case of the very long slender forms (Pl. 17, figs. 25, 26, and 
28) is more difficult, and the material at my disposal does not 
throw much hght on the question. 
LV. GENERAL REMARKS AND CONCLUSIONS. 
The life-history of Trypanosoma vittate shows a 
close resemblance to that of T. raiz. Some quite recent 
observations upon this last mentioned Trypanosome made in 
November, 1908, at the Millport Marine Station with Pontob- 
della which I had reared from the egg, have amply confirmed 
Brumpt’s brief sketch of the early stages of the life cycle.” 
Moreover, skate’s blood, which contained the ‘l'rypanosome 
kept upon sealed slides has shown that here also the Try- 
panosome discards its flagellum and undergoes a number of 
divisions. ‘I'he process is similar to that of 'T. vittate, but 
the rounded non-motile stage seems very much more per- 
sistent. In the Pontobdella motile flagellate stages do not 
‘ Tt is very difficult to be certain that division never takes place in 
this form, but I have never seen any sign of it. 
2 «©. R. Soe. Biol.,’ ix, 1906. 
