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Show 282 DR. F. DAY ON INDIAN FRESHWATER FISHES. [May 14, at its edge; the first and fourth arches have not even the rudiment of a gill. The branchial function is transferred to a receptacle on each side of the head above the branchial arches, covered by the upper part of the opercular membrane ; these receptacles have a cellular and highly vascular internal surface ; the cavity communicates with the mouth by an opening between the hyoid and the first branchial arch, and receives its blood from the terminal bifurcation of the branchial artery, and also from the different vessels ot the rudimentary gills. Those from the supplemental lung-like vascular sacs are collected into two trunks, which unite with the posterior unbranched branchial arteries to form the aorta. Ihus about one-half of the volume of the blood transmitted from the heart is conveyed to the aorta without being exposed to the action of the air." . Those who have seen these fish captured will scarcely admit their being usually sluggish. They lie about the sides of ponds in the grass, and are taken by means of baskets which the natives thrust down over them, when they can get near enough ; but before this is accomplished there is almost invariably an exciting chase, as they are very active in their movements. Much of the great tenacity of life for which many of the Indian freshwater fishes are famed is, no doubt, owing to their capability of respiring atmospheric air. As an instance of this may be adduced the Anabas scandens, which the fishermen in Calcutta are known to keep four or five days in earthen pots without water, using daily what they require, the fish being as well and lively as when caught. In fact the Calcutta market appears to be chiefly supplied with these fishes from extensive marshes in the Yasur district, and about 150 miles distant, whence boat-loads are brought and kept alive without water until sold*. In experiments made with these fish at Cochin, I found that they would live without moisture for about 24 or 26 hours. In India the majority of inland Acantho-pterygians are compound breathers-as, for example, the whole of the hollow-headed fishes, as well as many Siluroids and some of the Loaches. This method of respiration appears to be a wise provision of nature, to enable the fish, during periodic dry seasons, to migrate from pond to pond in search of water in which their natural food still exists. The possession of the means necessary for locomotion on land, combined with those for aerial respiration, frequently leads to their sudden appearance in unexpected places, and has given rise to numerous arguments and theories-amongst them spontaneous generation, vivification of buried ova, migration, falling from the clouds, &c. Many instances of the migration of fishes by land, from one piece of water to another, have been recorded. On the commencement of the rains in the east, the fish become very excited and disturbed, ascending small streams, & c , and, apparently dissatisfied with the waters they inhabit, restlessly seeking other localities. This may be due to the same instinct which causes the migration of marine * Hamilton Buchanan, ' Fishes of the Ganges,' p. 99. |