pretty correctly the average size of sea-trout on their second migration from the sea.”  In this state they usually make their appearance in our rivers, (we refer at present particularly to those of Scotland,) in greatest abundance in the months of May and June.  This view of the progress of the species clearly accounts for a fact well known to anglers, that in spring and the commencement of summer, larger sea-trout are caught than in July and August, which would not be the case if they were all fish of the same season.  But the former are herlings which have descended, after spawning early, to the sea, and returned with the increase just mentioned; the latter were nothing more than smolts in May, and have only once enjoyed the benefit of sea bathing.  They are a year younger than the others.

As herlings (sea-trout in their third year) abounded in the river Nith during the summer of 1834, Mr Shaw marked a great number (524) by cutting off the adipose fin.  “During the following summer (1835) I recaptured sixty-eight of the above number as sea-trout, weighing on an average about two and a half pounds.  On these I put a second distinct mark, and again returned them to the river, and on the next ensuing summer (1836) I recaptured a portion of them, about one in twenty, averaging a weight of four pounds.  I now marked them distinctively for the third time, and once more returned them to the river, also for the third time.  On the following season (23d day of August 1837) I recaptured the individual now exhibited, for the fourth time.[26] It then weighed six pounds.”  This is indeed an eventful history, and we question if any Salmo trutta ever before felt himself so often out of his element.  However, the individual referred to must undoubtedly be regarded as extremely interesting to the naturalist.  It exhibits, at a single glance, the various marks put upon itself and its companions, as they were successively recaptured, from year to year, on their return to the river—­viz. 1st, The absence of the adipose fin, (herling of ten or twelve ounces in 1834;) 2dly, One-third part of the dorsal fin removed, (sea-trout of two and a half pounds in 1835;) 3dly, A portion of the anal fin clipt off (large sea-trout of four pounds in 1836).  In the 4th and last place, it shows, in its own proper person, as leader of the forlorn hope of 1837, the state in which it was finally captured and killed, of the weight of six pounds.  It was then in its sixth year, and, representing the adult condition of this migratory species, we think it renders further investigation unnecessary.

    [26] The specimen is preserved in the Museum of the Royal
    Society of Edinburgh.