W. S. Patton and C. Strickland 
327 
with young leeches it was found that in one particular batch from one 
parent a large percentage developed an intense flagellate infection, while 
of another batch of young leeches fed on the same infected frog not 
a single one developed these flagellates, although exactly the same 
species of leech was used. It was eventually found that the explanation 
was quite simple: if the parent leech had flagellates in its alimentary 
tract a large percentage of its young also had them, whereas if the 
parent was not infected, its young also never developed flagellates. It 
was further impossible to trace any connection between these flagellates 
and the frog trypanosomes; we therefore believe they are true leech 
flagellates which are transmitted hereditarily. It is interesting to note 
that the flagellates developed in the leech from 2 to 4 days after feeding, 
exactly as in the case of the flagellates of G.fusca, and the small round 
forms of the leech flagellate were nearly always found in the anterior 
diverticula of the crop of the leech (cf. findings of Stuhlmann in 
G.fusca). So that in spite of the fact that Stuhlmann examined the 
other organs, presumably also the ovaries of G. fusca, we believe that 
the flagellate of this fly is transmitted hereditarily. We know it is 
exceedingly difficult to demonstrate the parasites in the eggs so that 
unless they were specially searched for at a particular stage they may 
readily be missed. In support of our view we would point out that 
Stuhlmann never found encysting forms similar to those of T. grayi in 
the rectum of G. fusca. Further Stuhlmann makes no reference to 
control experiments, that is to say feeding flies for the first time on 
animals known to be quite clean; we also note that no mention is made 
of the examination of the alimentary tracts of pupae of G.fusca descended 
from flies infected with flagellates. On examining Stuhlmann’s figures 
(Plate X, figs. 151 to 158) we are unable to see what connection the 
flagellates represented have with Trypanosoma brucei. Figures 152 a to g 
are described as trypanosomes from a heavily infected fly; of these a is 
a good picture of a young dividing Crithidia, b another form showing 
the growth of the flagellum ; the remaining figures c to g represent 
elongated Crithidia undergoing division; it is interesting to compare 
these figures with those of Crithidia gerridis. The proof as to how 
T. brucei comes to develop into these forms is in our opinion entirely 
wanting in Stuhlmann’s work. 
In a recent paper Keysselitz and Mayer (1908) claim to have fully 
confirmed Stuhlmann’s observations on the development of T. brucei in 
Glossina fusca. These authors at the outset refer to Prowazek’s work 
on the development of T. leiuisi in Haematopinus spinulosus ; we have 
Parasitology i 21 
