THE HJIMOFLAGELLATES. 311 



plete circle. It is fusiform in shape, and the anterior end is shorter and 

 rather blunter than in (say) T. soleae, while the posterior extremity is 

 drawn out and tapering. The undulating membrane has many well- 

 developed folds. (V.) hosts, Scyllium caniciila and S. stellare (catu- 

 lus), dogfish. 



T. rajse, Laveran and Mesnil. This form is, if anything, even larger 

 than T. scyllii, being from 75 — 80^ long, by 6/x wide. The free part of 

 the flagellum is about 20 ft. The shape and appearance of the parasite 

 agree in general with that of the last form, but the anterior extremity is, 

 usually, more tapering, and may, indeed, be very attenuated and proboscis- 

 like (fig. 62b). (V.) hosts, Rajaclavata, R. macrorhynchus, K. 

 mosaica, and R. punctata. Laveran and Mesnil consider that the Try- 

 panosomes found in these different rays all belong to the same species. (I.) 

 host, probably Pontobdella muricata, of frequent occurrence on infected 

 rays. 



Trypanosomes, probably distinct species, have also been observed in other 

 Piscine hosts, but not adequately described. Thus Valentin, in 1841, 

 noticed a Hismatozoan parasite in a trout (Salmo f ario) which, to judge 

 from his account, was in all likelihood a Tiypanosome, this being the first 

 recorded observation of such. In addition, Trypanosomes which have still 

 to be identified have been mentioned at various times as occurring in the 

 perch, gudgeon, and certain members of the Siluridse (e.g. Macrones 

 seenghala, M. tengara, Ophiocephalus striatus, and Trichogaster 

 fasciatus). 



APPENDIX. 



(a) Doubtful Trypanosomes. 



There are one or two parasites which have been relegated to tliis group of 

 organisms which appear to be not really Trypanosomes. Thus, there is the 

 form originally described by Eberth in 1S61 from the caecum and ileum of 

 poultry (liens, geese, ducks, etc.), which was named by Kent (27) T. eberth i. 

 This parasite is now generally thought to be a Trichomonas. 



Much more important is the organism described by Certes (143) in 1882 as 

 Trypanosoma balbianii. This parasite occurs in oysters and other 

 bivalves (Ostrseaedulis, 0. angulata, Tapes decussata, and T. pul- 

 lastra), where it inliabits the digestive tube, including the crystalline style 

 (fig. 63 b). All who have written on tliis form have agreed that it has no 

 free flagellum, but possesses, apparently, an undulating membrane (figs. 63 a 

 and c). Its length may be relatively enormous, from 50 jj, or less up to 150 /«, 

 but it is extremely thin, only from 1 — 3 /^ wide. The two most recent 



