602 



FAMILY: TRYPANOSOMID^ 



had been able to infect pike and eels by injecting blood from infected fish. 

 Very few attempts, however, have been made to infect fish with trypano- 

 somes from other species. Lebailly (1906) made some experiments of this 

 nature without success. Robertson (1911) found that the trypanosome of 

 the goldfish, perch, and bream could be transmitted to goldfish by the leech. 

 Transmission. — In nature, the trypanosomes of fish are carried by 

 leeches (Fig. 244). Some attempts by Minchin (1909) to infect the crus- 

 tacean Argulus by placing them on fish gave no result. 



Fig. 245. — Piscicola geometra, Dorsal and 

 Ventkal Views (x 3), Transmitter of 

 Trypanosomes and Trypanoplasms of 

 Fresh Water Fish. (After Harding, 

 1910.) 



Fig. 246. — PontobdeUa muricata, 

 the Transmitter of Try- 

 panosomes OF Marine Fish 

 (Natural Size). (After 

 Harding, 1910.) 



As long ago as 1857 Leydig had noted the presence of flagellates in the 

 stomach of the leeches {Piscicola and PontobdeUa) which had fed on fish, 

 and Doflein (1901) suggested the possibility of these invertebrates being 

 vectors of the fish trypanosomes. Keysselitz [cited by Hofer (1904)j 

 was able to transmit the trypanosomes of tench, carp, and pike by means 



