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 

 anuni." 



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 is thus 

 thrown on the branchiae. This will account for the fact that when 

 the fish is in a state of quiescence it lives much longer than when 

 excited, whilst the sluggishness sometimes evinced may be due to 

 poisoned or carbonized blood. 



Later investigations, especially those of X. J. Zograf on Pohjnran- 

 Ihns in 1888, have confirmed these results. 



The suprabranchial or epibranchial organ varies ni complexity 



fish with 

 Gourami, Os- 



>^ 



Fig. 97. — Branchial apparatus of 

 labyrinthiform pharyngeals, the 

 phromenus purami: a, articular process of epi- 

 branchial; c, copula or basibranchials ; I, laby- 

 rinth-plates of epibranchial of first branchial 

 arch ; m, muscular process of epibranchial ; p, 

 pharyngeals; y, basihyal ; 1, Hypobranchial ; 2, 

 Ceratobranchial ; 3. Epibranchial ; 4, Epipharyn- 

 geals or Upper pharyns^eals. 



