XVIIl] LIFE-CYCLE 3^9 



Monkey 113. 



Percentage 

 + 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 „ ,, ,, ,, — 



24 Numerous trypanosomes in blood + 



,, 25 „ „ „ „ ., + 



,, 26 Very numerous trypanosomes in 



blood . . . . . . — 89 o 



27 Very few trypanosomes in blood No flies fed — — 



28 / No trypanosomes seen in blood Flies fed 



29 \ both days 25 o 

 , , 30 Few trypanosomes in blood — 340 



31 ,, ,, ,, ,, + 107 i'8 



Sept. 1-3 Not examined 



4 Very few trypanosomes in blood — 32 o 



5 M ,, ,, ,, ,, 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 21 



9 Fair number of trypanosomes 



bul? much fewer than on 8 th No flies fed — — 



10 Not examined .. .. No flies fed — — 



11 Few trypanosomes 



12 Trypanosomes vey numerous 



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



13 Trypanosomes very numerous 



indeed .. .. .. No flies fed 70 14 



14 Trypanosomes very numerous 



indeed ...... ,, — — 



15 Blood swarming with trypano- 



somes ...... -f- 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 io-6 per cent., 

 which is remarkably high, for Bruce, Hamerton, Bateman 

 and Mackie found that the normal proportion of infected flies 



