228 E. A.: MINCHIN. 
ense in G. palpalis during the earliest periods of infection. 
A number of tsetse-flies freshly caught near Entebbe were 
fed on Monkey 420. Smears were made at the same time 
of the monkey’s blood. Four of the flies were dissected 
one hour after feeding, and four more five hours after feed- 
ing. . 
The monkey’s blood examined fresh showed trypanosomes 
fairly abundant, some more slender, active, others stouter, 
less active. In smears fixed with osmic vapour, well-marked 
differentiation of slender, stout, and intermediate forms were 
Seen (see P, R.1S., B 78, Pl. XT, figs. 16=19)0) A count 
gave 45 slender (8 dividing), 48 intermediate (8 dividing), 
and 3 stout forms. . 
In the smears from the flies dissected after one hour similar 
types of trypanosomes were seen, but the differentiation into 
slender and stout forms appeared to be more pronounced, 
and fewer intermediate forms were seen (figs. 36-39). The 
impression given by comparison of the monkey’s blood with 
smears made from the fly at this stage is that the intermediate 
forms of the former have become converted for the most part 
into the stouter type of the latter. A count gave 37 slender 
forms (6 dividing), 13 intermediate forms (2 dividing), and 
18 stout forms. 
Smears from the flies dissected five hours after feeding 
showed the differentiation still further advanced, especially 
of the slender forms, some of which showed the characteristic 
clear cytoplasm free from granules. Stout forms were also 
found (figs. 40-44). A count gave 21 slender forms (3 divid- 
ing), 6 intermediate forms (1 dividing), and 11 stout forms 
(1 dividing). 
Aug. Ist (twenty-four hours after infection).—Four flies 
were dissected, but smears were only made of two. The 
smears, both of the red and black blood, showed sharp differen- 
tiation into clear slender and granular stout forms (see 
P. R.S., B 78, Pl. XII, figs. 1, 2, 10, and 11). A count gave 
45 slender (7 dividing), and 13 stout forms (1 dividing). 
Aug. 2nd (forty-eight hours after infection)—Three flies 
