BLOOD-FARASiTES OF FISHES OCCURRING AT ROVIGNO. 135 



the possibility of considerable variation in size and appear- 

 ance^ and as a result have given fresh names to parasites 

 which are in all probability only phases of trypanosonies 

 already known from the same or closely allied hosts. We 

 have little doubt that Neumann has made such a mistake in 

 distinguishing his "Trypanosoma variabile'^ from T. 

 raias of skates. 



III. T. KAI^ FKOM RaIA SP. 



(Figs. 32-38, 52-57, and 66-68.) 



As this parasite has been described already by several 

 workers^ we need not give a general account of it here. One 

 or two points of interest have been observed, however, which 

 may be mentioned. In the fish examined the trypanosomes 

 were exceedingly abundant, but no dividing forms were seen, 

 nor were any hasmogregarines found. 



With regard to the behaviour of the trypanosomes in 

 freshly taken blood under a cover-slip, we found that they 

 remained alive and active for a much longer period than did 

 T. triglae kept in a quite similar condition. Many were 

 seen quite unaltered, but undergoing less active momeuts, 

 after twenty-four hours. Also after fifty-four hours several 

 were seen, their movements being now sluggish. At the end 

 of seventy-two hours only four were found, two of theni 

 being individuals which had been noted and marked after 

 twenty-four hours. They showed no alteration, but their 

 movements were very slow and feeble, being contined to little 

 jerks of the tiagellum and a very slight twistiug of the body. 

 Three of these individuals were seen again on the fourth day, 

 after ninety-six hours, when they appeared in much the same 

 condition. Lastly, on the fifth day one trypanosome only 

 was still seen living, extremely feeble and moving very slightly 

 at intervals. The remarkable point is that none of these para- 

 sites showed any alteration in form; nor during the earlier 

 periods, when several individuals were still ahve and fairly 



