NOTES ON ICHTHYOLOGY. 27 



Fish presumably therefore do sleep but lightly and seldom. Do fish hyber- 

 nate ? naturally follows the remarks on sleep, and again I cannot but assert 

 that I believe some do, and that nearly all are capable of doing so. The 

 well-known instance of the Ceylon mud fish, and fish of other waters in 

 India, which bury themselves during the dry season and emerge on the 

 rains filling the watercourses and hollows, is sufficient to show that at 

 least one fresh- water fish indubitably hybernates. Again, the eel retires 

 in winter to either the still deep and warm parts of the water, or buries 

 itself in the mud in a lethargic condition, to be revived at the approach- 

 of spring. The tench also occasionally may be found buried almost 

 completely, and I have, before now, taken him from the mud in a state 

 resembling the lethargy of complete hybernation as exhibited by the 

 dormouse or bat. Gold seems the chief agent in producing this state, and 

 Franklin recites a case in which some perch were frozen completely hard, 

 and were so brittle as to be easily broken, but were afterwards resuscitated 

 on being gradually thawed. Instances of the same kind, but unfortunately 

 not quite so well and definitely observed, have come within my own 

 experience. In the example given by Franklin it is impossible to avoid 

 the conclusion that remarkable vital powers under total suspension of 

 animation were exhibited. The sum of evidence is that such power by 

 the bye, the existence of an analogous power in warm blooded animals 

 is not proved to be impossible is possessed generally by cold blooded 

 creatures. The famous, and in some cases well authenticated stories of 

 the " toad in the hole," or in the middle of trees, brick walls, &c., are 

 forcible circumstances not to be forgotten. It should be added that the 

 gills of such fish as seem fitted for hybernation, partial or entire, have 

 opercula or gill covers with a membrane capable of being almost entirely 

 drawn over the opening. The object of this seems to be the retention of 

 moisture, and the preservation of the branches from impurity calculated 

 to injure the texture. 



The capacity for living out of water is very great in some specimens of 

 fresh- water fishes. The carp is not infrequently in Germany and other 

 continental countries kept suspended in nets, the only necessary condition 

 being that a continual but not copious supply of fresh water be thrown 

 over the body of the fish. Fish so treated are said to be fed on bread 

 soaked in milk with occasionally a little brandy added. I have known 

 perch to live twenty-two hours in a cool damp situation out of water, and 

 I believe that eels, if carefully kept damp, would live longer. 



The diseases of fish are many, and chiefly parasitic. Not only are the 

 parasitic growth animal, but they are of vegetable growth also. 



The internal parasites of fish are in number legion. A complete list 

 would be a herculean task, as may be inferred from the statement of Dr. 



