22 NOTES ON FISH AND FISHING. 



thing equivalent to it. And this is brought about by- 

 disease and the legitimate wiles of anglers and the illegi- 

 timate wiles of poachers. The Diseases of Fish offer too 

 wide a field for me more than cursorily to allude to them 

 here. Like the poor bull in Virgil's Georgics, they suffer 

 many bodily ailments, though they " play no tricks " with 

 their bodies, as we civilized men and women do. They 

 are victims especially to internal and external parasites, 

 the former afflicting them most. Of the internal para- 

 sites, nearly all those found in the intestines of fish are only 

 in the first stage of their life-cycle, which is not fully de- 

 veloped until they have passed into the bodies of birds 

 or quadrupeds, and in some cases into the human system 

 itself. Dr. Cobbold, in the Synopsis of the Bistomidm, 

 says that of the 344 species of "fluke" (or trematoda), 

 no less than 126 are found in fish, and that this species 

 of entozoa are " particularly plentiful in the stickleback, 

 minnow, tench, perch, pope, trout, salmon, and still more 

 abundant in pike, barbel, and bream." The gyrodactylus 

 elegans attaches itself to the gills and fins of the last- 

 named fish; anguillulidce, of the order of Mematoda, or 

 round worms, are found in nearly all fresh-water fish : 

 the " thorn-headed " worms are the special bane of roach, 

 and to be afflicted with Echinorhynchidce, as roach and 

 trout are, to the wasting of their poor bodies, sounds as 

 terrible an affliction as Elephantiasis in the human being. 

 The Oestoda, or tapeworm, is another most common para- 

 site in the intestines of our fresh-water fish, and some- 

 times creatures of this species when measured are found 

 as long as the fish from which they are taken. Then 

 again there is Ligala dignamma, which afflicts many fish, 

 especially barbel, and renders their blood nearly colour- 



