XVIII] LIFE-CYCLE 39 



Monkey 113. 



Percentage 



f or - of flies 



Condition of blood examined laboratory bred Number of becoming 



Date alive flies flies fed infected 



Aug. 20-22 No trypanosomes seen in blood No flies fed 



23 Few ,, ,, ioi o 



,, 24 Numerous trypanosomes in blood + 45 IIT 



25 ' + 53 37 



,, 26 Very numerous trypanosomes in 



blood 89 o 



27 Very few trypanosomes in blood No flies fed 



28 J* No trypanosomes seen in blood Flies fed 



,, 29 \ both days 25 o 



,, 30 Few trypanosomes in blood 34 o 



31 ,, ,, ,, + I0 7 ** 8 



Sept. 1-3 Not examined 



4 Very few trypanosomes in blood 32 o 



5 ,, ,, ,, ,, ,, No flies fed 



6 Moderate number of trypano- 



somes, dimorphism of broad 



and narrow forms very marked 49 o 



7 Moderate number of trypano- 



somes . . . . . . No flies fed 



8 Trypanosomes very numerous 



indeed ...... + 95 2'i 



9 Fair number of trypanosomes 



but much fewer than on 8th No flies fed 

 ,, 10 Not examined . . . . No flies fed 



,, ii Few trypanosomes 



,, 12 Trypanosomes vey numerous 



indeed . . . . . . + 70 1-4 



,, 13 Trypanosomes very numerous 



indeed . . . . . . No flies fed 70 i -4 



14 Trypanosomes very numerous 



indeed . . . . . . ,, 



15 Blood swarming with trypano- 



somes ...... + 20 10 



infected with T. gambiense by laboratory bred flies. The bush- 

 buck had harboured the trypanosome for about fifteen months. 

 This monkey shewed infective and non-infective periods in 

 exactly the same way as other infections, but the infective 

 periods gave a remarkably large percentage of flies harbouring 

 trypanosomes. Out of 150 G. palpalis that were fed on this 

 monkey, 16 became infected, a percentage of 10-6 per cent., 

 which is remarkably high, for Bruce, Hamerton, Bateman 

 and Mackie found that the normal proportion of infected flies 



