ECOLOGY, COMMENSALISM AND PARASITISM 381 



Trypanosoma species, in Polypterus sp., Neave, 1906. 



Trypanosoma species, in serpent head, Mathis and Leger, 1911. 



Trypanosoma species, in Siluris glanis, Keysselitz, 1906. 



Trypanosoma squalii, in Squalus cephalus, Brumpt, 1906. 



Trypanosoma strigaticeps, in Plecostomus strigaticeps, da Fonseca and Vaz, 



1928. 

 Trypanosoma synodontis, in Synodontis notatus, Leboeuf and Ringenbach, 



1910. 

 Trypanosoma tincae, in tench, Laveran and Mesnil, 1904. 

 Trypanosoma toddi, in Clarias anguillaris, Bonet, 1909. 

 Trypanosoma torpedinis, in torpedo, Sabarex and Muratet, 1908. 

 Trypanosoma triglae, in tubfish, Neumann, 1909. 

 Trypanosoma yakimovi, in pipefish, Wladimiroff, 1910. 

 Trypanosoma zungaroi, in Pseudopimelodus zungaro, da Fonseca and Vaz, 



1928. 



This formidable list of species of trypanosomes is not complete, 

 but zoologically more than nine-tenths of these are probably 

 synonyms. A useful purpose is served by the mere mention of a 

 species of trypanosome in a new host, and until the life history of 

 each is worked out the synonym may be ignored. 



The term Trypanosoma was first used by Gruby (1843) as a 

 generic name for blood parasites which, earlier, were regarded as 

 amebae. Little attention was paid to the genus until mammalian 

 trypanosomes w r ere discovered. Attention was particularly drawn 

 to these by Lewis, studying rats in Bombay as a possible means of 

 distributing the plague, when he found active organisms in the 

 blood. Smears were made and sent to Saville Kent for identifica- 

 tion. Still more important was the discovery of a mammalian 

 disease associated with trypanosomes in the following year by 

 Evans, who found peculiar organisms in the blood of horses and 

 mules in India with a disease called surra. Smears were likewise 

 sent to Kent who identified them as the same organism as that found 

 by Lewis, and he included them both in his genus Herpetomonas, 

 species leivisi. The correct interpretation of these as Trypanosomes 

 followed a few years later. A great advance was made by Bruce, 

 in 1893, who demonstrated the agency of tsetse flies (Glossina mor- 

 sltans) in transmitting the disease nagana to cattle, while human 

 trypanosomiasis and its transmission by tsetse flies (Glossina pal- 

 palis) was fully established by the observations on Gambia fever 

 of Forde (1901), Button (Tryp. gambiensi) (1902), of Castellani 

 who was the first to see trypanosomes in sleeping sickness; and of 

 Bruce (1903) who showed that Gambia fever is an initial stage of 

 sleeping sickness, and that, like nagana, the trypanosome is trans- 

 mitted by a tsetse fly. Later discoveries showed the presence of 

 trypanosomes in every group of vertebrates (see list, p. 372), many 

 of them producing fatal diseases, while transmission by various 

 kinds of invertebrate hosts— sand flies, biting bugs, mosquitoes, 

 fleas, lice, mites, ticks and leeches — has been established. 



