. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PARENTAL CARE AMONG FRESH-WATER FISHES. 527 cavities to receive these appendages. It was fonnorly iwstiilated that this apparatus had the office of receiving and retaining supplies of Avater which should trickle down and keep the gills moist; such Vv-as supposed to be the adaptation for the sustentation of life out of the water. The experiments of Surgeon Day and others, however, threw doubt upon this alleged function and tend to show (1) t
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PARENTAL CARE AMONG FRESH-WATER FISHES. 527 cavities to receive these appendages. It was fonnorly iwstiilated that this apparatus had the office of receiving and retaining supplies of Avater which should trickle down and keep the gills moist; such Vv-as supposed to be the adaptation for the sustentation of life out of the water. The experiments of Surgeon Day and others, however, threw doubt upon this alleged function and tend to show (1) that these fishes die '' when deprived of access to atmospheric air, not from any deleterious properties either in the water or in the a})- paratus used, but from being unable to subsist on air obtained solel}' from the water, aerial respiration being indispensable;'" (2) "that they can live in moisture out of water for lengthened periods, and for a short and variable time in water only; " (3) " that the cavity or receptacle does not contain water, but has a moist secreting sur- face in which air is re- tained for the purpose of • respiration, and it seems probable that this air, after having been supplied for this purpose, is ejected by the mouth and not swal- lowed to be discharged per ; In fine, the two respira- tory factors of the bran- chial a})paratus have inde- p(3ndent functions: (1) the labyrinthiform or phar- yngeal portion being a special modification for the use of atmospheric air; (2) the gill filaments discharg- ing their normal function. If, however, the fish is kept in the water and prevented from com- ing to the surface to swallow the atmospheric air, the labyrinthiform ajjparatus becomes filled w^ith water, which can not be discharged owing to its almost noncontractile power. There is thus no means of emptying it, and the water probably becomes carbonized and unfit for oxygenizing the blood, so that the whole of the respiration
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