244 



Miss M. Robertson. Development of 



[Feb. 26, 



infected by wild flies from the lake-shore, first showed trypanosomes in its 

 blood on July 25, 1911. On August 23, Monkey 113 showed trypanosomes 

 in its blood ; 137 flies were fed in groups, 36 of these were treated as a 

 starvation experiment ; the whole series proved negative with the exception 

 of one starved cage, which showed one infected fly on the 12th day. On 

 August 24, 45 flies were fed on the same monkey, and there resulted five 

 infected flies, that is, a percentage of 11*1 showed trypanosomes. On 

 August 25, 53 flies were fed, of which two were infected, which is equal to a 



percentage of 3*7. 



Table I.— Monkey 113. 



Date. 



Condition of blood examined 

 alive. 



laboratory 

 flies. 



Number 

 of flies 

 fed. 



Percentage 

 of + flies. 



Number 

 of experi- 

 ment. 



Aug. 20 

 21 



No trypanosomes seen in blood . . . 



No flies fed 





~ 





„ 22 

 „ 23 

 „ 24 



„ 25 

 „ 26 



Few " " 

 Numerous trypanosomes seen in 



Very numerous trypanosomes in 

 Very few trypanosomes seen in 



[Showed no trypanosomes in J 

 J blood 



j-Not examined. 



+ 



101 



45 



53 



11 '1 

 3-7 



38—42 

 44 and 45 



46 

 47—49 



>, 2Y 



„ 28 



„ 29 

 „ 30 

 „ 31 



Sept. 1 

 2 

 3 



No flies fed 



(flies fed 

 both days) 



(box fed on 

 30thand31st) 



_ 

 25 



34 

 107 



_ 



1 -8 



_ 

 50 



55 and 56 

 54 



4 



Very few trypanosomes 





32 





58 



5 





No flies fed 









6 

 7 



., 8 



Fair number of trypanosomes ; 

 dimorphism of broad and 

 narrow forms very marked 



Fair number of trypanosomes . . . 



Trypanosomes very numerous 

 indeed 



No flies fed 



49 

 95 



2-1 



60 



62 and 64 



9 



„ 10 

 ., 11 



Fair number of trypanosomes, 



but much fewer than on 8th 

 Not examined. 



No flies fed 

 No flies fed 









» 12 



Trypanosomes very numerous 

 indeed 





70 



1-4 



68 



„ 13 

 „ 14 

 „ 15 



Blood swarming with trypano- 

 somes 



No flies fed 



20 



10 -o 



75 



On August 26, however, 89 flies were fed in three groups on this same 

 monkey, and produced no infected flies at all. The experiments ran con- 



