GRAYLING. 207 



gions, — one the Coregonus Signifer; and 

 another, which appears to differ very little 

 from it except being small in size. This 

 seems to agree as nearly as possible with 

 our grayling, with a difference of at most 

 one spine in the back fin. May not this in 

 fact be the same fish as the grayling of the 

 Alps, only rendered in a succession of gener- 

 ations fit for a colder climate ? 



Hal. — This is certainly possible: there is 

 no doubt, that, in many successive genera- 

 tions, animals may be fitted to bear changes, 

 which would have destroyed their progeni- 

 tors. It is said by Bloch, that graylings are 

 found in the Caspian Sea, and in the Baltic, 

 — masses of saline water ; though, as I have 

 proved, the grayling of England will not 

 bear even a brackish water, without dying. 

 And notwithstanding the severity of the 

 winter in high northern latitudes, streams 

 under the ice may retain a temperature not 

 much lower than some of the Alpine rivers. 

 I have seen grayling in Carniola, in a source 

 at the hottest season not quite 50° ; and as, 

 in large bodies of water, the deepest part, 

 in frost, is generally the warmest — about 



