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, Surgeon ELM. 

 British Forces, kindly undertook the care of the fish on their way 

 home, aud succeeded by great attention in bringing both alive to Dub- 

 lin. 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 motion- 

 less 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 



