TRYPANOSOMES IN TSETSE-FLIES AND OTHER DIPTERA. 213 
small forms almost exclusively in the proboscis, seldom in the 
gut, even in its most anterior parts ; for, as I have described 
above, the corresponding forms of T’. grayi are, on the con- 
trary, most abundant in the hindmost parts of the digestive 
tract. Ameoeboid forms, with flagella reduced or absent, are 
also described, and are stated to be present sometimes in great 
numbers, but only in hungry flies. They are regarded as rest- 
ing phases, and perhaps correspond to the round forms of 
T. grayi, but I have never seen anything like the “ giant 
amoeboids, with 4-16 nuclei,” figured by Stuhlmann (loc. 
cit., fig. 154). 
The following is the scheme of development suggested by 
Stuhlmann: The infection begins by a multiplication of 
indifferent forms in the intestine. From this point they 
spread forwards as far as the proventriculus, where Stuhlmann 
has seen and figured (loc. cit., fig. 102 a—g) appearances 
which he believes to be conjugation. After conjugation, 
probably, are produced the small forms, which may be the 
infective forms which pass back into a new vertebrate host. 
The nature of the long, slender forms is doubtful ; they appear 
simply to die out. In no cases were trypanosomes found in 
the end gut (proctodzeum), nor in the salivary glands, nor in 
any organs of the fly except the proboscis and the digestive 
tract proper—that is, as far back as the end of the intestine. 
The fact that Stuhlmann and Kudicke used only flies bred 
in the laboratory for their infection experiments may be 
taken as proof that the trypanosomes observed by them in 
these flies were truly stages of I’. brucii. Stuhlmann is of 
opinion, and I agree with him, that trypanosomes are not 
transmitted by tsetse-flies to their posterity ; in other words, 
that so-called germinative or hereditary infection does not 
occur.! Itis evident, then, that T’. brucii not only multiplies 
1 T cannot follow Novy (82) when he refers to the supposed occurrence of 
trypanosomes in tsetses that have never fed on animals; he even commits 
himself to the extraordinary statement that “only a very small percentage of 
biting insects ever feed on blood” (loc. cit., p. 406). I can only explain 
such an utterance om the part of an investigator so skilled aud experienced by 
