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Show 1874.] RESPIRATION OF FRESHWATER FISHES. 319 ceeded in pushing its body through the net at 3.30 P.M. : at 4 P.M. the same fish remained in a vertical position, having its head thrust through one of the meshes of the net, but not at the surface of the water. At the same time the M. pancalus lay on its side, moving the gill-covers with difficulty, and in fifteen minutes afterwards it died; twenty minutes afterwards, at 4.35 P.M., the Rh. aculeata died also. A specimen of M. pancalus placed in water with free access to the surface was, at the time of death of the other two, as lively as in the morning. I kept specimens of both Anabas scandens and Trichogaster fas-ciatus in an aquarium in my house at Calcutta for many months, and had constant opportunities for observing their habits. Two specimens of the Anabas which had lived in the aquarium from September 1871, were in April 1872 sent by me to the Gardens of the Royal Zoological Society of Ireland. Dr. Isidore Bourke, Surgeou H.M. British Forces, kindly undertook the care of the fish on their way home, and succeeded by great attention in bringing both alive to Dublin. One died three months after arrival, from an injury ; the other lived for nine months, and then succumbed to the cold. I am quite satisfied that had the water of the aquarium in which the fish lived in the Dublin Zoological Gardens been kept at a temperature of 75° Fahr., or at least not permitted at any time to fall below 60°, the surviving specimen would have lived (if otherwise uninjured) for many years. The habits of Anabas scandens and Trichogaster fasciatus are very similar. Both suddenly rush to the surface, discharge the vitiated air and take in a fresh supply instantaneously, immediately sinking to the bottom, where one or two bubbles of air may often be seen to escape from the gill-openings as if taken in excess. The action of discharging the air from the branchial cavities and taking in a fresh supply is accomplished so rapidly that it is impossible to say whether the used-up air is discharged before the fresh supply is taken in, or displaced by the incurrent stream of air. All that can be seen is, that when the fish places its mouth at the surface of the water a great quantity of air bubbles up about its head. The Trichogaster appears to use the long filiform ray to which the ventral fin is reduced as a tentacle, moving it about towards any passing object. I have often seen one of these fishes move forward this ray and touch with it another fish slightly in front and on the same side, while the ray on the other side remained perfectly motionless directed backwards. Like the Anabantes they are fond of chasing one another round and round ; and while so engaged the independent action of the single-rayed ventral fins as tentacles may be well seen. The number of visits to the surface appears to depend, as might be expected, on the amount of muscular action accomplished by the fish, and on the temperature of the water; thus, when actively engaged in chasing one another, and in very warm weather, the visits were very frequent, sometimes three or four times in five minutes. Of all the fish experimented upon the Anabas went oftenest to the |