134 J- A. MINCIIIN AND B. M. WOODCOCK. 



of 45 fi in tlie case of our fonn.i Further, tlie aflagellar 

 end of the body is short and somewhat blunt^ as indeed is 

 often the case in these " stumpy " types of trypanosome, and 

 the membrane does not show well-developed folds. 



At first sight these two trypanosomes, from different 

 species of Trigla, might be considered to belong without 

 doubt to different species ; and probably many authors would 

 not hesitate to give both parasites a distinct name. In our 

 opinion this would be decidedly premature, for we think it 

 quite likely that both are merely different forms of one and 

 the same species. Polymorphism is now known to be of 

 common occurrence among trypanosomes. To give only one 

 or two instances, Minchin (11) has recently shown clearly, by 

 photographs, the marked (sexual) polymorphism in T. gam- 

 biense, while one of us (H. M. W.) has been struck by the 

 polymorphism, of a character quite similar to that implied in 

 the case before us, which occurs in an Avian trypanosome. 

 We do not intend here to ascribe any special sexual signifi- 

 cance to the "stout " (wide) form of the Tri gl a trypanosome ; 

 we suggest, however, that Neumann's form is a particular type 

 of the parasite we have described above, the latter being the 

 one which we are inclined to regard as the more " ordinary " 

 type. Hence our reasons for including the trypanosome 

 from Trigla in the species T. triglse. 



In connection with this point, it may be remarked, it is 

 especially among piscine trypanosomes, where the parasites 

 attain to such large dimensions that marked variations in 

 form and appearance may be expected to occur, due either to 

 young forms or to different types of the parasite. It seems 

 to us that there has been too much tendency to ascribe hard 

 and fast limits to the size of a specific trypanosome. Many 

 authors, in describing new species, appear to have overlooked 



' It is quite possible that tlie real width is not so mucli as these 

 figures indicate ; for we liave found that it is especially in such stout or 

 stumpy types that flattening-out in dry smears may be most appreciable 

 and most liable to give an incoi-rect idea of the true width of the pai-a- 

 site. 



