As regards the fresh-water fishes of India and Ceylon, the fact is now established that certain of them possess the power of leaving the rivers and returning to them again after long migrations on dry land, and modern observation has fully confirmed their statements. They leave the pools and nullahs in the dry season, and led by an instinct as yet unexplained, shape their course through the grass towards the nearest pool of water. A similar phenomenon is observable in countries similarly circumstanced. The Doras of Guiana[1] have been seen travelling over land during the dry season in search of their natural element[2], in such droves that the negroes fill baskets with them during these terrestrial excursions. PALLEGOIX in his account of Siam, enumerates three species of fishes which leave the tanks and channels and traverse the damp grass[3]; and SIR JOHN BOWRING, in his account of his embassy to the Siamese kings in 1855, states, that in ascending and descending the river Meinam to Bankok, he was amused with the novel sight of fish leaving the river, gliding over the wet banks, and losing themselves amongst the trees of the jungle.[4] [Footnote 1: _D. Hancockii_, CUV. et VAL.] [Footnote 2: Sir R. Schomburgk's _Fishes of Guiana_, vol. i. pp. 113, 151, 160. Another migratory fish was found by Bose very numerous in the fresh waters of Carolina and in ponds liable to become dry in summer. When captured and placed on the ground, "they _always, directed themselves towards the nearest water, which they could not possibly see_, and which they must have discovered by some internal index. They belong to the genus _Hydrargyra_ and are called Swampines.--KIRBY, _Bridgewater Treatise_, vol. i. p. 143. Eels kept in a garden, when August arrived (the period at which instinct impels them to go to the sea to spawn) were in the habit of leaving the pond, and were invariably found moving eastward _in the direction of the sea_.--YARRELL, vol. ii. p. 384. Anglers observe that fish newly caught, when placed out of sight of water, always struggle towards it to escape.] [Footnote 3: PALLEGOIX, vol. i. p. 144.] [Footnote 4: Sir J. BOWERING'S _Siam,_ &c., vol. i. p. 10.] The class of fishes endowed with this power are chiefly those with labyrinthiform pharyngeal bones, so disposed in plates and cells as to retain a supply of moisture, which, whilst they are crawling on land, gradually exudes so as to keep the gills damp.[1] [Footnote 1: CUVIER and VALENCIENNES, _Hist. Nat. des Poissons_, tom. vii. p. 246.]