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Show 286 DR. F. DAY ON INDIAN FRESHWATER FISHES. [May H, n become depopulated. Again, the distance from other pieces o water at which they reappear, excludes in many instances the possibility of migration, which must always, to a certain extent, be regulated by distance, time, and other local circumstances. I have already shown that some species can live in liquid mud, which they cannot employ for the purposes of aquatic respiration. The question now arises whether, during the drought when food and water fail, fish do not altogether hybernate, or rather aestivate, until the return of a more favourable season. From their low state of organization, they would undoubtedly be more hkeiy to become torpid during the heat than many other animals possessed of a higher vitality, which have been proved to do so, such as the Batrachians, the Emys, the Lepidosiren annectens, some of the Crocodiles, and others, as well as mollusks and land-snails. The natives of India believe this to be the case; and many of them, and some few Europeans, have asserted that they have actually seen fishes thus exhumed alive from the bottoms of perfectly hard dry tanks, and subsequently resuscitated by placing them in water. That they are capable of burrowing is easily proved by watching them in an aquarium, and is especially exemplified in the case of a small Loach (Platacanthus madraspatensis, Day), which, if the water is being changed, or anything occurs to alarm it, dives down into the sand, and totally disappears from view with the greatest rapidity ; and so well does it conceal itself that, on several occasions, when the sand was removed from the aquarium, it was most difficult to find and capture it. It evidently employs its armed pectoral fin for the purpose of diving. The Etropli and many others also conceal themselves very rapidly and effectually when alarmed. It appears probable that, as the water in the tanks becomes low, the fishes congregate together in holes aud places in which some water still remains, where they may frequently be seen in numbers huddled together with only sufficient water to cover their dorsal fins. If disturbed they dive down into the thick mud, and if either a drag or cast-net be then employed it is probable that nothing will be obtained. The only way of catching fish at this time is to leave the net down and walk about in the surrounding thick mud. In the course of time they must come to the surface to breathe, and then they fall an easy prey. As the water gradually evaporates, the fishes appear to become more and more sluo-gish and finally, there is every reason to believe, bury themselves in the soft mud, and in a state of torpidity await the return of their natural element. This would, if proved, only show the correctness of Dr. Hunter's assertion*, "that hybernation is apparently due to a suspension of the faculties of animals by nature durino- s u ch seasons, and in such situations, that a supply of food is not obtainable." In Europe it is known that fish hybernate during the winter months. Eels bury themselves twelve or sixteen inches deep in the * Observations on Parts of the animal Economy, p. 88. |