immediate action of the shot.  They were about six inches under water.  Having obtained a sufficient supply of the impregnated spawn, he removed it in a bag of wire gauze to his experimental ponds.  At this period the temperature of the water was about 47 deg., but in the course of the winter it ranged a few degrees lower.  By the fortieth day the embryo fish were visible to the naked eye, and, on the 14th January, (seventy-five days after deposition,) the fry were excluded from the egg.  At this early period, the brood exhibit no perceptible difference from that of the salmon, except that they are somewhat smaller, and of paler hue.  In two months they were an inch long, and had then assumed those lateral markings so characteristic of the young of all the known Salmonidae.  They increased in size slowly, measuring only three inches in length by the month of October, at which time they were nine months old.  In January 1841, they had increased to three and a half inches, exhibiting a somewhat defective condition during the winter months, in one or more of which, Mr Shaw seems to think, they scarcely grow at all.  We need not here go through the entire detail of these experiments.[23] In October (twenty-one months) they measured six inches in length, and had lost those lateral bars, or transverse markings, which characterise the general family in their early state.  At this period they greatly resembled certain varieties of the common river-trout, and the males had now attained the age of sexual completion, although none of the females had matured the roe.  This physiological fact is also observable in the true salmon.  In the month of May, three-fourths of the brood (being now upwards of two years old, and seven inches long) assumed the fine clear silvery lustre which characterises the migratory condition, being thus converted into smolts, closely resembling those of salmon in their general aspect, although easily to be distinguished by the orange tips of the pectoral fins, and other characters with which we shall not here afflict our readers.

    [23] A complete series of specimens, from the day of hatching
    till about the middle of the sixth year, has been deposited by
    Mr Shaw in the Museum of the Royal Society of Edinburgh.

The natural economy of the sea-trout thus far approximates that of the genuine salmon, but with the following exception.  Mr Shaw is of opinion that about one-fourth of each brood never assume the silvery lustre; and, as they are never seen to migrate in a dusky state towards the sea, he infers that a certain portion of the species may be permanent residents in fresh water.[24] In this respect, then, they resemble the river-trout, and afford an example of those numerous gradations, both of form and instinct, which compose the harmonious chain of nature’s perfect kingdom.  In support of this power of adaptation to fresh water possessed by sea-trout, Mr Shaw refers to a statement by the late Dr McCulloch, that these fish had become