NOTES ON ICHTHYOLOGY. 29 



ever, as will be seen from the example I am about to cite. Some time 

 since, whilst walking by the side of Virginia Water, I perceived a roach, 

 apparently very faint dying, but not dead. It measured seven inches. 

 Its weakness was so extreme that I had no difficulty in capturing it. 

 On opening it I found the intestinal canal very much distended with 

 three tape worms, measuring respectively 5in., 6in., and 9in., by from 

 iin. to $in. broad. On examination no " hook appendages " or means of 

 attachment of any kind could be seen, nor was any movement perceptible. 



Dr. Cobbold kindly communicated its name to me as Ligula digramma 

 of Creplin. The effect on the fish was most disastrous. The blood and 

 there was but very little was nearly colourless, the fins pallid, the eye 

 abnormally yellow, and a malignant pustule (similar to that which afflicts 

 the carp) was to be detected appearing on various parts of the skin. I 

 have before and since observed the same parasite which completes its 

 development in the heron usually in trout, perch, and eels, and doubt 

 not that it is very common in all still waters. The sexual development of 

 the carp (Cyprinus carpio) remains arrested, whilst another species of 

 this worm (Ligula simplicissima) resides in the abdominal cavity ; and 

 this fact may possibly account for the assertion of Gesner, that some 

 carp which came under his notice were sexless. 



An instance has been recently stated by Professor Sterling, of Edin- 

 burgh, in which 96ft. of tapeworm were taken from the pyloric gut of a 

 salmon. 



The external parasites are no less curious and worthy of attention, from 

 the fact that their presence is often a valuable indication to the angler of 

 the " condition " of his quarry, and from their frequent great microscopical 

 beauty. 



They may be divided into two classes, viz., vegetable and animal ; and 

 although the distinction is in some cases hardly perceptible, yet, as it 

 undoubtedly does exist, cognizance must of course be taken of it. Apart 

 from the fact, however, no special importance attaches to it at this 

 time. 



Of the vegetable organisms found parasitic on fish there is considerable 

 variableness as to form and development, according to the seasons, a 

 hard winter being sufficient to almost utterly destroy the more delicate 

 species, and thus in some instances proving extremely beneficial to certain 

 fishes the barbel, for example, a fish peculiarly liable to parasites of 

 all kinds. On the other hand, a mild winter and early spring are as 

 favourable as severe cold is disastrous, to this form of vegetation. 



There are great numbers of differing growths unclassified and practically 

 unknown, but for advantages of examination and beauty of development, 

 perhaps the little plant Achlya prolifera, usually to be found on the 



