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much bigger than the others. In a big fish like a cod, it is a large, firm calcareous stone, which can be easily found by any one who likes to do a little dinner-table dissection when the head of a boiled fish is served. Dr. Lee, an American naturalist, has suggested that the ear-sacs and stones have nothing to do with hearing but serve the fish in perceiving movements through space such as rotation and loss of equilibrum. After many experiments with dogfish, in which the canals or the auditory nerves were cut, he has been able to produce strong evidence that the ear is an organ closely connected with the sense of equilibrium. If the otoliths or ear-stones are removed from one ear, the fish's balance is interfered with to a considerable extent. The removal of otoliths from both ears practically destroys all sense of equilibrium. An attempt has been made to connect the three stones with movements through the three dimensions of space but this has not been very convincing. There is, however, a general opinion now that fish which, with few exceptions,

* Dr. Lee's paper will be found in the Journal of Physiology for 1894, vol. xv.

are dumb, are also deaf to ordinary sounds. The connection between their internal ears and lateral lines has clearly been traced. It would seem that ears were not evolved to hear delicate vibrations of sound until animals became breathers of air.

Lastly, there remain to be described the lateral lines and other mysterious sense-organs of fishes about which not much is known. Whether they are organs of touch or taste or means of perceiving vibrations in the water is not clearly decided. That fish are sensitive to touch is obvious, even when they are covered with horny scales, but the most delicate parts are about the snout, where special organs, barbels, are developed. The lateral line which is conspicuously marked in many fish, and is sometimes differently coloured, is a tube with small openings at regular intervals which perforate the scales. One purpose of this tube is certainly to secrete slime, and it is sometimes called the mucous canal system. The lateral line continues up to the head, but is less conspicuous there. It passes under the skin and a series of connected tubes pass along the ridges of the forehead, cheeks, jaws and eyes. They

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still communicate with the surface of the skin by pores and produce mucous. The canal is provided with special nerves and sensory cells. It is looked on as a sense-organ, but what purpose it serves has not been clearly established. It is, without doubt, adapted to the conditions of aquatic life, because the fish-like tadpoles of frogs and other amphibians have a lateral line which is lost in the mature animal which lives on land. Its use is very problematical, but probably, besides secreting slime, it enables the fish to perceive waves of vibration in the water. The relationship of the internal ear with the lateral line confirms this view. It may be that the power of perceiving wave vibrations which must be strongly felt in water, enable the fish to feel the approach of its prey or its enemies. That this would be of the greatest service to fish both large and small, cannot be doubted. "Master," says the fisherman in Pericles (Act II., sc. 1), "I marvel how fishes live in the sea." To which the older fisherman answers: "Why, as men do a-land; the great ones eat up the little ones."

Very closely allied to the sense-organs of the

lateral line are structures known as end-buds. They are, in fact, a number of sensory cells compacted into a mass shaped like a flower-bud and connected with the nervous system. In lampreys and fishes they are scattered over the surface of the body. In the highest land-animals they are confined to the inside of the mouth and it is such structures as these which enable us to taste. It may well be that fishes, living as they do in water, are capable of tasting with their external skin.

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It seems, then, that the main thing is to keep out of sight when one is fishing, for the eyes of the trout are its chief defence against the approach of an angler on the bank. With very shy trout in shallow streams, and no growth of herbage along the bank, this is really the greatest difficulty with which the fisherman has to contend. second difficulty, also dependent on the trout's sense of sight, is the gut-shy fish which makes off as soon as the fly falls. This terror, produced by gut floating over a trout's head, increases in marked fashion as the season goes on if the water has been at all fished. It is a problem worth

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considering whether the trout's movements under these conditions are due to conscious or reflex action. It is strange, however, that where trout are very constantly fished for they become more regardless of the gut and go on feeding steadily. They seem to trust to their powers of discriminating between natural and artificial flies. One day it probably comes to pass that they make a mistake.