Even those smolts which descend together in April and May, (the chief periods of migration,) do not agree in size. Many are not half the length of others, although all have assumed the silvery coat. "I had, last April," Mr Young informs us in a letter of 3d June 1843, "upwards of fifty of them in a large bucket of water, for the purpose of careful and minute examination of size, &c., when I found a difference of from three and a half to six inches--the smallest having the same silvery coat as the largest. We cannot at all wonder at this difference, as it is a fact that the spawn even of the same fish exhibits a disparity in its fry as soon as hatched, which continues in all the after stages. Although the _throng_ of our smolts descend in April and May, we have smolts descending in March, and as late in the season as August, which lapse of time agrees with the continuance of our spawning season. But in all these months we have an equal proportion (that is, a corresponding mixture) of large and small smolts. I have earnestly searched for smolts in the winter months, year after year, and I can only say that I have never seen one, although I have certainly tried every possible means to find them. I have seen fish spawning through the course of six months, and I have seen smolts descending through the same length of time. Our return of grilses, too, exactly corresponds with this statement. Thus a few descending March smolts give a few ascending May grilses; while our April and May swarms of smolts yield our hordes of grilse in June and July. After July, grilses decrease in numbers till October, in proportion to the falling off of smolts from May to August. At least these are my observations in our northern streams." They are observations of great value, and it is only by gathering together similar collections of facts from various quarters, that we can ultimately attain to a clear and comprehensive knowledge of the whole subject.