365 
H. L. Duke 
Of the gut-only infections a certain number were due to T. grayi, but all 
the positive flies were not examined in stained preparations. 
Infectivity data obtained by dissection are, of course, more exact than 
those from fly-feeding experiments. It is interesting, however, to note that 
the same figure for the infectivity of wild Damba flies in 1920 is obtained 
by fly-feedings as by dissection, i.e. 0-08 per cent. 
The observations set forth in subsections (a) and ( b ) show that the in¬ 
fectivity of the wild G. palpalis of the Uganda lake-shore to the polymorphic 
trypanosome has remained remarkably constant throughout the last 12 years. 
(c) Gr. morsitans dissections in Uganda and Nyasaland. 
The following figures were obtained by the dissection of G. morsitans in 
the Northern Province and are given for comparison (Duke, 1916): 
Total dissected 
... 1117 
Flagellates in proboscis only 
... 8-5% 
„ proboscis and gut 
... 3-1% 
„ gut only 
... 1-6% 
„ gut and glands 
... 0-17% 
In Nyasaland the Commission working with G. morsitans found the flies 
infected as follows (Bruce, 1914 b ): 
1912— Total dissected ... ... ... 1975 
Flagellates in gut and glands ... 0-1 % 
1913— Total dissected ... ... ... 1060 
Flagellates in gut and glands ... 0-09 % 
The infectivity with the polymorphic trypanosome, as revealed by fly feedings 
in the Northern Province and Nyasaland respectively, was 0-59 per cent, 
and 0-2 per cent. 
(d) The trypanosomes of palpalis regions in Uganda and elsewhere. 
The absence of the nanum-pecorum group of trypanosomes from the wild- 
fly of the Uganda lake-shore is remarkable. In the course of dissections made 
in the inland districts of the Protectorate, T. nanum was detected in 1-4 per 
cent, of 713 palpalis dissected from the Northern Province, but was not 
found in 477 flies from the Western Province (Duke, 1913 c?). At Mpumu 
T. nanum was transmitted by laboratory-bred flies, but both this trypanosome 
and its near ally T. pecorum seemed to find great difficulty in developing in 
this tsetse (Duke, 1912 a , and Fraser, 1912). It is almost certain that these 
trypanosomes were introduced into Sesse in cattle in the old days, together 
with T. brucei. After the raids of 1895 into Bukedi, cattle from this ynorsitans 
area reached the islands; the trypanosomes have, however, not established 
themselves. Proboscis-only infections amounted to 3*0 per cent, in the 
Northern Province fly but were not seen in flies from the Western Province. 
No trypanosomes of the polymorphic group were obtained from 1333 
palpalis tested by feeding in the Northern Province. In the Western Province, 
