364 Mammalian Trypanosomes of Africa 
Damba the percentage is just a little higher than formerly, but the totals 
are too small to warrant any conclusion. 
The effect of the settlement of antelope on an island previously free from 
these animals and carrying only hippopotamus, reptiles, otters, and birds is 
well shown by the two Nsadzi experiments (k) and (l). 
The small number of flies infected with the polymorphic organism is 
striking, and should be compared with the figures obtained with laboratory- 
bred flies set forth in Section V. 
(b) Dissections of wild flies. 
Mainland. 
Nov.-Dee. 1920. Proboscis; glands, and gut examined. 
Total dissected . 299 184, $ 115) 
Flagellates in gut only ... ... 28 i.e. 9-3 % (<$ 20, $ 8) 
„ proboscis or glands ... 0 
Zinga Island, near the mainland. Dec. 1920. 
Total dissected 
Flagellates in gut only 
„ proboscis or glands 
48 (<J 10, $ 38) 
10 i.e. 20-8 % 
0 
Sesse Islands other than Damba. Dec. 1920. 
Total dissected 
Flagellates in gut only 
,, proboscis 
,, gut and glands 
307 (<? 263, $ 44) 
15 i.e. 4-8 % (<? 14, $ 1) 
3 i.e. 0-9 % 
0 
Damba Island. Sept. 1920. Gut and glands only dissected. 
Total dissected . 490 (<$ 423, $ 67) 
Flagellates in gut only ... ... 0 
Of these flies all save 183 had fed over-night on a clean monkey. 
Damba Island. Dec. 1920. Gut and proboscis dissected, glands examined only if any 
flagellates seen. 
Total dissected 
Total containing flagellates 
In gut only 
In proboscis only 
In gut and glands 
695 
30 i.e. 4-3 % 
2 i.e. 0-28 % 
27 i.e. 3-8 % 
1 i.e. 014 %* 
* The monkey fed upon by this fly became infected. 
Of the above flies all save 117 had fed over-night on a monkey. 
Total percentages for Damba Island: 1185 flies. 
Gut only . 0-16 % 
Gut and glands ... ... 0-08% 
In the dissections, as with the fly-feeding experiments, the main object 
was to determine the proportion of flies infected with the polymorphic 
trypanosome. Proboscis infections give an additional indication of the extent 
to which the flies feed on antelope. 
All the infected proboscides showed flagellates in the hypopharynx, and 
usually a few loose in the labrum. In four flies there were big fixed clusters 
in the labrum. 
