102 
Haemqftagellates, etc. 
very untidy description we gather that this trypanosome merely under¬ 
goes a process of multiplication exactly similar to that of T. lewisi, 
T. rotatorium, and others in cultures. We cannot regard this as a true 
developmental cycle and therefore the leech cannot be a true alternate 
host; no sexual cycle appears to be necessary. We note there is 
no mention of the possibility of the leech in question having a natural 
flagellate in its alimentary tract; perhaps Miss Robertson will show in 
her next paper that such a flagellate has been carefully excluded. If 
not we must doubt even this method of multiplication of T. vittatae. 
All the above authors in their researches on the development of 
piscine and reptilian trypanosomes and trypanoplasmes in leeches have 
failed to exclude their natural flagellates; their descriptions also of the 
various life cycles are far from convincing. Some of the parasites appear 
to have a sexual cycle, while others have dispensed with the sexual pro¬ 
cess, and merely multiply asexually. Much of the work requires 
confirmation and reinvestigation. It is quite unjustifiable to draw any 
far-reaching conclusions from what we consider to be erroneous 
observations. 
With regard to Prowazek’s (1905) work w'e have recently criti¬ 
cised it and shown that there is no evidence to support the view that 
T. lewisi undergoes a developmental cycle in Haematopinus spinulosus ; 
we consider Prowazek’s developmental forms represent a part of the life 
cycle of a true Critliidici of the louse. Referring to the development of 
other mammalian trypanosomes in tsetse flies, Woodcock describes the 
work of Minchin, Gray and Tulloch. Minchin (1908) in a recent paper 
has drawn attention to the polymorphism exhibited by T. gambiense in 
the blood of a rat; two of the types he regards as sexual forms ; there is 
however no proof that this view is correct. It has yet to be proved that 
these types represent male and female trypanosomes. We do not think 
there is the slightest evidence that these so-called male and female 
parasites conjugate soon after they pass into the stomach of an insect. 
Stuhlmann (1907), in his work on the development of T. brucei in G.fusca, 
has not described the male, female, and indifferent forms of the parasite 
of Nagana as depicted by Prowazek (1905); nor does he refer to the 
formation of ookinetes at the beginning of the infection of the fly. The 
first parasites he found in G. fusca were of the neutral type, which 
occurred in large numbers in the midgut of the fly. Woodcock thinks 
Stuhlmann probably missed some early essential phases of the develop¬ 
ment, for Leger found ookinetes of T. barbatulae in the leech eighteen 
hours after it had fed. According to Stuhlmann the indifferent para- 
