512 



Dr. C. Morley Wenyon 



[March 3, 



Though trypanosomes give rise to sleeping sickness in man and 

 produce similar diseases in domestic animals, these hosts, as I ex- 

 plained before, are not to be regarded as the natural hosts, which are 

 actually the wild game upon which tse-tse flies also feed. Similar 

 trypanosomes occur in many other animals, and they are commonly 



Fig. 5. — A Trypanosome of a Fish, and its development in a leech, 

 a Trypanosome in the blood of the fish. (Magnified 1500 times.) 

 p-s Diagram of the development in the leech, 

 s, stomach of the leech containing multiplying trypanosomes ; p, proboscis of 

 leech surrounded by the cavity of the proboscis sheath containing infective 

 trypanosomes which have made their way there from the stomach by 

 passing through the mouth at the end of the proboscis. 



b, c, d Development of the trypanosome in the leech. (Magnified 1500 times.) 

 b, developmental forms in the stomach ; c, elongate forms in the proboscis 



sheath ; d, trypanosome form which enters the fish through the wound 



made by the proboscis. 



