370 PHILOSOPHY OF ZOOLOGY. 



the surface of the ponds in which they are kept are frozen 

 over, the various kinds of fish seem to contract diseases, 

 and, in such cases, great mortality often prevails. This 

 seems to arise from want of air in the water, and can only 

 be prevented by removing the fish to a deeper pond, 

 through which there is a constant current. In some rigo- 

 rous seasons, the extent of this mortality is most alarming, 

 an example of which occurred between 1788 and 1789, 

 when the inhabitants of some districts of France lost near- 

 ly all their stock of carp, pike, and tench. Journal de 

 Physique, November 1789. * 



" None of the fish have ever bred ; indeed, no opportunity of breeding is af- 

 forded^to them. A warm and shallow retreat, laid with sand and gravel, would 

 have to be prepared for some species ; and large stones, with sea-weed grow- 

 ing on them, would have to be transferred to the pond, and placed so as to 

 be constantly immersed in the water for the use of others. The dimensions 

 of the present pond, however, are two circumscribed to admit of its being 

 used as a breeding place. An addition for this purpose might, without much 

 difficulty, be formed, and here some curious observations might be made. 

 The spawn of various sea-fishes is frequently accidentally dredged up by fish- 

 ermen, and, could, therefore, no doubt, be procured by using a dredge : its 

 degree of transparency indicates whether it will prove prolific. This might 

 be placed in a protected corner of the breeding pond, and its progress watch- 

 ed. On this branch of the natural history of sea-fishes, little is known." 



* In the beginning of the year 1789, Mr BAKER states, that carp were 

 taken out of a pond where the ice was broken, frozen crooked and stiff, with- 

 out the least motion, and ice hanging about them ; but being laid on dry 

 straw in a cellar they all recovered." Phil. Trans, 1791. p. 92. In the 

 same year, an epidemic distemper affected even those fish which live in the 

 sea, as the following fact, communicated by the late Mr CREECH of Edin- 

 burgh, in the Appendix to the sixth volume of the Statistical Account of 

 Scotland, satisfactorily proves: " On Friday, 4th December 1789, the ship 

 Brothers, Captain STEWART, arrived at Leith from Archangel. The captain 

 reported, that on the coast of Lapland and Norway, he sailed many leagues 

 through immense quantities of dead haddocks floating in the sea. He spoke 

 several English ships, who reported the same fact." Other evidence is 

 stated by the Rev. Cooper Abbs. Phil. Trans. 1792, p. 367. 



