170 SALMONIA. 



Poiet. — You just now said, that you 

 thought the Lapland fish considered by 

 Linnaeus as the grayling, was the same as 

 Back's grayling; but I find in the Appendix 

 to Capt. Franklin's narration, two graylings 

 described as belonging to the northern re- 

 gions, — one the Coregonus Signifer, and 

 another which seems to differ very little from 

 it, except being small in size. This seems 

 to agree as nearly as possible with our gray- 

 ling, 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 generations 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 Block, 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 



