Classification of Fish—Their Form and Colour—Mode and Means of Life—Curiously-shaped Fish—Senses of Smell and Hearing in Fish—Fish nearly Insensible to Pain—The Fecundity of Fish—Sexual Instinct of Fish—External Impregnation of the Ova—Ripening of a Salmon Egg—Birth of a Herring—Proposal for a Marine Observatory in order to note the Growth of our Sea Fish—Curious Stories about the Growth of the Eel—All that is known about the Mackerel—Whitebait: is it a Distinct Species?—Mysterious Fish: the Vendace and the Powan—Where are the Haddocks?—The Food of Fish—Fish as a rule not Migratory—The Growth of Fish Shoals—When Fish are good for Food—The Balancing Power of Nature. Fish form the fourth class of vertebrate animals, and, as a general rule, they live in the water; although in Ceylon and India there are found species that live in the earth, or, at any rate, that are able to exist in mud, not to speak of some that are said to occupy the trees of those countries! The classification of fishes as given by Cuvier is usually adopted. That eminent naturalist has divided these animals into those with true bones, and those having a cartilaginous structure; and the former again are divided into acanthopterous and malcopterous fish. Other naturalists have adopted more elaborate classifications; but Cuvier’s being the simplest has in my opinion a strong claim to be considered the best; at least it is the one generally used. A fish breathes by means of its gills, and progresses chiefly by means of its tail. This animal is admirably adapted for progressing through the water, as may be seen from its form, which has been imitated more or less closely by the builders of ships, the makers of weavers’ shuttles, and others. Fish are exceedingly beautiful as regards both form and colour. There are comparatively few persons, however, who have an opportunity of seeing them at the moment of their greatest brilliancy, namely, just when they are brought out of the water. I allude more particularly to some of our sea fish—as the herring, mackerel, etc. The power of a fish to take on the colour of its hiding-place may be mentioned. I found, a few weeks ago, some young fish of various kinds in the Tweed at Stobo, which were, when in the water, quite undistinguishable from the vegetable matter among which they were taking shelter. It is not an easy matter to paint a fish so as accurately to transmit to canvas its exquisite shape and glowing colours. The moment it is taken from its own element its form alters and its delicate hues fade; and in different localities fish have, like the chameleon, different colours, so that the artist must have a quick eye and a responding hand to catch the rapidly-fleeting tints of the animal. Nothing, for instance, can reveal more beautiful masses of colour than the hauling into the boat of a drift of herring-nets. As breadth after breadth emerges from the water the magnificent ensemble