'27S DR. F. DAY ON INDIAN FRESHWATER FISHES. [May \4, 



(Bloch), of the respective sizes of 5^, 4^, and 3^ inches in length, 

 were placed at 6.30 in the glass globe of a hanging lamp measuring 

 10 inches across and 12 inches deep ; this was filled two-thirds full 

 of fresh water, the temperature being 75° Fahr. A diaphragm of 

 net was then stretched tightly across the diameter one inch below 

 the water, thus effectually preventing the fish from rising to the 

 surface to obtain atmospheric air. At the end of four minutes they 

 all became excited, and pushed vigorously against the net, which, 

 however, they did not succeed in breaking. They continued at 

 intervals to make these ineffectual efforts, but at 8. 1 a.m. the smallest 

 sank down and died, at 8.2 a.m. the medium-sized one, and at 8.8 a.m. 

 the largest. Thus the largest and strongest only lived one hour and 

 twenty-eight minutes when deprived of direct access to atmospheric 

 air. On opening their gills under water and pressing the branchiae 

 no air escaped from the cavity. 



ExiKviment No. 2. — To prove satisfactorily that death did not 

 ensue either from deleterious properties in the water or from the ex- 

 clusion of air by the diaphragm, three more were placed at 8.45 a.m. 

 in the same vessel in which the others had died, the water not having 

 been changed ; it was covered over with the same diaphragm at about 

 an inch above the water. The temperature was then 76°, at 1 1 a.m. 

 76°, 12 a.m. 80°, 4 p.m. 78°, 6 p.m. 7S°, 10 p.m. 78°; and, to pre- 

 vent recapitulation, it may be as well to state that these temperatures, 

 unless otherwise specified, prevailed throughout these experiments. 

 But in this case the fish, heing able to reach the air, did well and 

 were taken out the next day, after they had been left in the same 

 water for 24 hours. 



Experiment No. 3. — Three specimens of Siluroid water-breathers 

 {Macrones tengard) were placed in the same globe similarly prepared 

 as in the first experiment. After 25 hours they were as lively and 

 well as when first put in. It was impossible for them to have ob- 

 tained atmospheric air direct ; but they swam as near the surface as the 

 diaphragm would permit, which may easily be accounted for by the 

 great heat of the water, and the comparatively small amount of 

 fluid contained in the globe. Subsequently this experiment was 

 tried with some Cyprinidse, two specimens of Puntius stigma (Cuv. 

 & Val.), one oi Amblypharyngodon jerdoni, all water-breathers, and 

 three Loaches {Platacanthus agrensis). The water-breathers re- 

 mained unaffected ; but the Loaches died in eight hours. This genus 

 of Loaches have a receptacle for air in the first vertebrae, which cir- 

 cumstance was overlooked when I first described them*. 



Experiment No. 4. — Three more specimens of Ophiocephalus 

 punctatus were placed in some wet grass in an earthen vessel, in 

 which they were kept for upwards of three hours, or double the 

 length of time it took to drown those excluded from atmospheric air 

 and thus compelled to breathe water only. At the end of this time 

 they were all alive and healthy. 



Experiment No. 5. — Another specimen of the Ophiocephalus punc- 

 tatus was held under water, and as much air as possible evacuated 

 * Proc. Zool. Soc. 1865, p. 298. 



