of smell, that salmon-roe used to be a deadly trout-bait, but fishing with salmon-roe is now illegal. It has been said by some naturalists that fish do not hear well, but that assertion is contrary to my own experience; for on making repeated trials as to the sense of hearing in fish, I found them as quick in that faculty as they are sharp in seeing; and have we not all read of pet fish being summoned by means of a bell, and of trouts that have been whistled to their food like dogs? Water is an excellent conductor of sound: it conveys a noise of any kind to a greater distance, and at nearly as great a speed as air. Benjamin Franklin used to experiment on water as a conductor, and soon arrived at the conclusion that its powers in this way were wonderful. By striking two stones together, the experimenter will find that the sound is conveyed to a great distance, and also that it is very loud. Most kinds of fish are voracious feeders, and prey upon each other without the slightest ceremony; and the greatest difficulties of the angler are experienced after the fish have had a good feed, when even the most practised artist, with his most seductive bait, will not induce them to nibble, far less to bite. Many of our fish have a digestion so rapid as only to be comparable to the action of fire, and in good feeding-grounds the growth of a fish usually corresponds to its power of eating. In the sea there exists an admirable field for observing the cannibal propensities of the fish world, where shoals of one species have apparently no other object in life than to chase another kind with a view to eat them; and what goes on in the sea on a wholesale scale is imitated on a smaller scale in the loch and the river. To compensate for the waste of life incidental to their place of birth and their ratio of growth, nature has endowed this class of animals with an enormous power of reproduction. Fish yield their eggs by tens of thousands or millions, according to the danger that has to be incurred in the progress of their growth. All fish are enormously fecund; indeed there is nothing in the animal world that can in this respect be compared to them, except perhaps a queen bee, which has fifty or sixty thousand young each season; or the white ant, which produces eggs at the rate of fifty per minute, and goes on laying for a period of unknown duration; not to speak of that terrible domestic _bug_bear which no one likes more particularly to name, but which is popularly supposed to become a great-grandfather in twenty-four hours. The little aphides of the garden may also be noted for their vast fecundity, as may likewise the common house-fly. During a year one green aphis may produce one hundred thousand millions of young; and the house-fly produces twenty millions of eggs in a season!