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Show 318 MR. G. E. DOBSON ON THE [May 19, face. Having accomplished this it remained tranquil, resting on the upper surface of the net. The same fish was, on the following day, replaced in the same jar and the net strengthened. The animal remained tranquil for five minutes, then became uneasy and dashed about violently, several bubbles of air passing upwards from the gill-openings. Occasionally it would remain quiet at the bottom for one or two minutes, then become very uneasy, and struggle powerfully against the net. Half an hour after immersion the fish became even more energetic in endeavouring to break the net, but soon became weaker, and died in 1 hr. 10 min. Repeated the same experiment with three smaller-sized specimens of the same species. Immediately after the diaphragm had been fixed the fish rose and attempted to reach the surface, striking violently against the net. They then sank to the bottom, and during the first half hour frequently renewed their attempts to reach the surface. One of the fishes thrust its head through one of the meshes of the net and was retained in that position. The other two died at the same time, in 1 hr. and 5 min. (lying at the bottom in 10 inches of water) ; the third fish (which was retained in the mesh of the net near the surface, above which it did not, however, get its mouth) died twenty-five minutes afterwards. The experiment was again repeated. Two specimens of the same species were placed in about 6 inches of water, with a perforated metal plate half an inch beneath the surface. They struggled in precisely the same manner, and then lay at the bottom for some minutes, the gill-covers moving slowly and with difficulty. Struggled violently one hour after the diaphragm was fixed, and died in 1 hr. 35 min. Exp. 10.-A specimen of Ophiocephalus punctatus, 4 inches in length, was placed in the same glass jar at 1.55 P.M. ; at 2.10 P.M. it rose towards the surface and pushed against the net; at 3.30 P.M. it feebly endeavoured to reach the surface, but soon sank down exhausted. Respiration appeared to have entirely ceased; a large bubble of air passed upwards from its mouth; and it died three minutes afterwards. Another specimen of the same species was subjected to the same experiment. The fish became much excited after being placed in the water, and swam about rapidly, striking against the netting for about two or three minutes. It then sank to the bottom and remained quiet. On being roused up ten minutes afterwards it again rose and made many energetic attempts to reach the surface, during which a bubble of air escaped from its mouth. It again sank to the bottom and remained there, the gill-covers moving very slowly. Death occurred in 4 hrs. 40 min. The mouth was widely opened towards the time of death. Exp. 11.-At 11 A.M. placed a specimen of Mastacembelus pan-calus and one of Rhynchobdella aculeata in the glass jar, fixing the netted diaphragm as hi preceding experiments. Both the fishes made several attempts to reach the surface; the R. aculeata nearly sue- |