28 On Flukes. 



inquiry are embodied in a lengthened " Synopsis of the Disto- 

 midas," published in the fifth volume of the "Journal of the 

 Proceedings of the Linneean Society " In that communication 

 344 different species of flukes were recognized; and of these, 

 126 are proper to fishes, 47 to reptiles, 108 to birds, 58 to 

 mammalia, and 5 to non- vertebrate d animals. This list, how- 

 ever, does not include certain leech-like forms of fluke (such as 

 are described by parasitologists, under the generic titles of 

 Tristoma, Poly stoma, Gyrodadylus, and the like), the greater 

 part of which ought rather to be considered Ectozoa than 

 Entozoa, inasmuch as their habit is to attach themselves to the 

 external surface of the bodies of the creatures they attack. No 

 doubt, in the above record, many immature forms have been 

 regarded in the light of distinct species by the older authors ; 

 but when, on the other hand, we take into consideration the 

 additions which have been recently made — especially by Pro- 

 fessor Molin of the University of Padua and by the writer 

 himself — and also the probably much larger number of forms 

 which remain undiscovered, it becomes evident that, at the 

 very lowest estimate, we may assume the order Trematoda to 

 comprise five hundred species. 



Flukes are small animals, usually visible to the naked eye, 

 but seldom attaining any very significant bulk, some of the 

 minutest forms scarcely exceeding the y^ of an inch in longi- 

 tudinal diameter. The species most commonly known (Fasciola 

 hepatica) is capable of attaining a length of rather more than 

 an inch, and there are four other flukes whose measurement is 

 considerably beyond this. These four notables, deserving 

 special mention, are the following : — 



1. The Distoma crassum, fourteen of which were discovered 

 by George Busk, Esq., F.P.S., in the alimentary canal of a 

 Lascar. The original description states that "these flukes were 

 much thicker and larger than those of the sheep, being from 

 an inch and a half to near three inches in length." One 

 example may be seen in the Museum of the Eoyal College of 

 Surgeons, Lincoln's Inn ; and a second in the Museum of the 

 Middlesex Hospital Medical College. 



2. The Distoma veliporum, procured by Professor Otto, of 

 Breslau, from the stomach of a large Mediterranean shark 

 (Squalus griseus). This fluke acquires a length of fully three 

 inches. 



3. The Fasciola gigantea, a trematode of equal longitude, 

 and rather broader than the last named. Forty specimens 

 were found by the writer in the liver of a young giraffe, which 

 died in Womb well's travelling menagerie, at Edinburgh, during 

 the severe winter of 1854-55. 



4. The Distoma gig as, discovered and described by the 



