458 PARASITES OF ANIMALS 



of Salmo umbla, D. longum (Leidy) from the pharynx of Esox 

 estor, D. polymorphism from the urinary bladder of the common 

 pike (Esox Indus), D. obesum from the gall bladder of Salminius 

 and other Brazilian fishes (Xiphostoma, Leporinus), D. tornatum 

 attached to the gills of Coryphana hippuris, D. rosaceum attached 

 to the palate of Lota communis, and D. contortum attached to 

 the gills of Orthagoriscus mola. Most of the forms found 

 encysted are sexually-immature worms. To these belong 

 D. annuligerum, found by Nordmann in cysts in the vitreous 

 humour of the eye of the perch (Perca fluviatilis) , andD. embryo 

 from the liver and peritoneum of Acerina vulgaris. One of the 

 largest and most remarkable of the flukes inhabiting marine 

 fishes is the Distoma clavatum, found by Tilesius in the stomach 

 of Pelamys, by Pohl in Thynnus, and by Bosc in CorypJwena. 

 In the last-named fish it has been found adhering to the gills, 

 in the liver, and in the intestines. In August, 1865, 1 obtained 

 this parasite from a sword-fish (Xiphias gladius), and in the 

 same piscine host I also found examples of four other species 

 of helminths (Tetrarhynchus attenuatus, scolex of another tetra- 

 rhynch, Bothriocephalus plicatus, Ascaris incurva). Believing 

 Distoma clavatum to represent several forms hitherto regarded as 

 distinct, I append a few particulars respecting it. Five examples 

 of this worm were obtained by me from the stomach of a sword- 

 fish. Generally they varied in length from four lines to two 

 inches. They differed somewhat in shape, but all had the so- 

 called head and neck directed backwards. Below the ventral 

 sucker the two largest specimens were distended with eggs 

 and black pigment. All of them likewise exhibited more or 

 less well-marked transverse rugae, the last ring surrounding 

 an orifice which represented the outlet of a large contractile 

 vesicle. The eggs averaged 8 Jo" in length. 



When revising the entozoa of the Museum of the Royal 

 College of Surgeons I encountered many parasites without 

 labels attached. Amongst these were several flukes, which, 

 though differing from each other in size and shape, appeared to 

 be identical. One of these specimens turned out to be the 

 particular Distoma clavatum described and figured by Professor 

 Owen in the 'Zoological Society's Transactions/ Several of 

 the others I made out to be part of a series contributed by Mr 

 George Bennett, who also gave specimens to the British 

 Museum, but the College Museum stores contained yet a third 

 group of specimens of uncertain history. The large fluke 



