A DEGENERATE GLAND. — PRINCE. 203 



strata are of necessity imperfectly oxygenated, and unless 

 disturbed by moving currents, unable to support the higher 

 forms of animal life. As was shown by observations in the 

 Swedish hsheries, the presence or absence of the usual schools 

 of certain fish was almost solely influenced by the greater or 

 less amount of water rich in oxygen pouring into the Baltic 

 Sea from the open ocean. Active migratory fishes, such as 

 mackerel and herring, must be largely controlled b}^ these 

 conditions, especially in waters more or less inclosed or separated 

 from the open oceanic areas. 



The line of thought here opened up is one of great practical 

 as well as scientific importance ; but I have treated elsewhere* 

 of this and cognate matters aflecting the environment of fishes 

 and need not say more in this place. Nitrogen, as compared 

 with oxygen, is of inferior moment in the vital processes, 

 especially the respiratory processes, of the animal frame ; but 

 the amount of oxygen present in the swim-bladder, especially 

 in fishes whose circumstances would seem to demand an ample 

 •'^^^PPb'' ^'^ ^^^ insignificant in quantity to ba important in the 

 oxidation phenomena going on in those organisms. The nature 

 of the gases, which occupy the chamber of the sv/im-bladder 

 would, indeed, seem to be wholly unimportant physiologically 

 and dependent upon contingent circumstances. Fishes without 

 a swim-bladder have, at any rate, no corresponding storage of 

 gases. 



The object of this paper is to show how little support 

 prevailing theories (as to a hydrostatic, respiratory, barometric, 

 accoustic, or other function) receive from the facts, and that 

 whatever adaptations the swim-bladder may undergo, it is 

 clearly not primarily in function either hydrostatic, accoustic, 

 or sound-producing, respiratory, barometric, or for balancing or 

 floating purposes simply. I would point out in the first place 

 this most remarkable fact that, without exception, the anatomists 

 who have treated of the functions of this organ, have ignored 



*Xo. 18. p. xlviii. 



