FROM A SWORD-FISH. 201 



of them likewise exhibited more or less well-marked transverse 

 rugse, extending from tlie root of the ventral sucker to the lower 

 end of the body. The last ring thus formed surrounded a distinct 

 caudal orifice, representing the outlet of a largely developed con- 

 tractile vesicle. The eggs presented an average longitudinal 

 diameter of y-^". Some other points bearing upon the question 

 of specific difference will be incidentally mentioned below. 



AVhen recently occupied in revising the collection of Entozoa 

 contained in the Museum of the Eoyal College of Surgeons, I 

 encountered a considerable variety of parasites without any labels 

 attached, or any mark capable of guiding one as to the source of 

 the specimens. Amongst these were several flukes, which, though 

 differing from each other in respect of size and shape, appeared 

 to be identical species. One -of these specimens I afterwards 

 found to be the actual Distoma clavaUmi described and figured 

 by Professor Owen in the Zoological Society's Transactions. 

 Several of the others I have since (by comparing them with spe- 

 cimens deposited in the British Museum) clearly made out to be 

 part of a series contributed by Mr. Greorge Bennett ; but the Col- 

 lege Museum-stores contained yet a third group of specimens, 

 whose history has hitherto evaded all my endeavours to unravel it. 

 The large individual described by Professor Owen was formerly in 

 the collection of the Eev. Lansdowne Gruilding ; but we do not 

 know from what fish it was obtained. In Dr. Baird's catalogue, the 

 specimens presented by ISIr. Bennett are stated to have come from 

 the stomach of the Bonito ; and it is not improbable that Mr. 

 Guilding's specimens, as well as many others whose history is 

 wanting, maybe referred to the same " host." Be that as it may, 

 however, the specimens in question not only diff'er very markedly 

 among themselves, but also, in some respects, from many other 

 forms referable to the same species. I here allude to the various 

 specimens described by systematists, some under one title and 

 some under another. In fact, a species-splitter can point to five 

 or six tolerably distinct forms, which in my view ought to be re- 

 garded as specifically identical. To prove this, however, it is 

 necessary to investigate the matter with some care, and to pass in 

 review all the more important notices which have from time to 

 time appeared. 



In the year 1730, M. Grarsin, a surgeon in the employ of the 

 Dutch East-Indian Company, and Corresponding Member of the 

 Erench Academy of Sciences, first described this worm, under the 

 generic title of Sirudmella. He says : — " Cet insecte tire de 



