4662 Fishes. 



a good deal of their natural heat, from being carried in my pocket : I fancy the 

 state of the atmosphere had a good deal to do with it. The feathers of the bird next 

 day showed no signs of electricity." Are feathers in general so electrified? or does 

 this happen in certain stales of the weather? If you would kindly furnish me with 

 any information on these points, you would much oblige. — Id. 



Some Observations on the Salmo Estuarius or Estuary Trout. 

 By R. Knox, M.D., F.R.S.E., &c. 



Many esteemed naturalists still view certain members of the natural 

 family of the Salmonidae as mere varieties, dependent for their origin 

 and permanency on the influence of the surrounding media in which 

 they have been accidentally placed. In respect of some of these so- 

 called varieties such a view is probably the correct one ; but having 

 for many years adopted other views as to the origin of species, the 

 relations of species to natural subfamilies, and of these again to natu- 

 ral families or genera, and having lately tested these views by an 

 appeal to the principles of transcendental anatomy, I continue to view 

 as distinct species many races or kinds of animals which others look 

 on as mere varieties. 



Amongst these I place a race or kind of trout which I have ventured 

 to call the estuary trout (Salmo Estuarius), simply because I have 

 hitherto found it to frequent chiefly those waters " into which the tide 

 ebbs and flows," waters very difficult to define, a fact which many pro- 

 prietors of salmon rivers have learned to their cost. The term 

 " estuary " will not, I hope, be objected to on the ground that there 

 are many rivers which have no estuary, and in which this species of 

 trout may notwithstanding be found, my meaning being merely this — 

 that the trout in question inhabits those waters, and those waters only, 

 influenced by the tide; the brackish waters, in fact, of rivers whose 

 limits neither naturalists nor engineers, lawyers nor chemists have 

 been able rigorously to define. 



The trout I am now to describe is a fine and delicate fish, with all 

 the beauty of the class or natural family to which it belongs. It in- 

 habits the brackish waters or estuary, and I have never found it higher 

 up in the rivers towards their sources, and only twice in the sea. 

 Those I have examined, and they have been very numerous, were 

 mostly taken with the net near the mouth of the Tyne of East Lothian, 

 in North Britain, and in the Nith of Dumfriesshire (also in Scotland), 



