i893. BIOLOGICAL THEORIES. 353 



intensity of a sound (wliatever its pitch) is proportional to the range 

 of pressure through which the transmitting medium passes during 

 the transmission of the wave. Making allowance, however, for this 

 error, the result would be the same. The intensity of wave, in water, 

 necessary to produce a vibration of one-thousandth of an inch would 

 in air produce a movement of about ten inches, and would involve 

 changes of pressure which the human skull could certainly not resist, 

 whether the walls of the building could or could not. 



"Otocyst" is a name given to a sac, usually microscopic, lined 

 with a sensory epithelium, usually, if not always, provided with 

 sensory hairs. The sac encloses an "otolith," that is, a mass of 

 some substance (usually calcareous) denser than the surrounding 

 water or the tissues of the otocyst. The otolith may be replaced by 

 several masses of some dense solid. 



These, as the name "otocyst" signifies, are regarded, if not by 

 all, at least by most zoologists, as auditory organs, and their action 

 is said to depend upon the jolting of the hairs against the otolith or 

 (which is worse !) vice versa. 



Perhaps what has been written above may convince zoologists 

 that the production of any such jolting by an aquatic sound-wave is a 

 physical impossibility. It is barely conceivable that any wave should 

 involve pressures so great as to reduce the volume of any mass of 

 substance to absolutely nothing, that is, to cause the matter of which 

 it is composed to cease to exist. No pressure short of this would, 

 however, bring the otolith into contact with the sensory hairs in 

 question, even if they were, to begin with, at an infinitesimal 

 distance. The fluid pressures we have to do with act equally in all 

 directions. No movement, except in the direction of the wave- 

 propagation, is produced : there can be no flowing outwards to the 

 sides of even an infinitesimal amount of water which was between 

 the tip of the hair and the otolith, for the pressure at the sides 

 is equal to that between the hair-tip and the otolith. 



Whatever the function may be of such organs as otocysts, tenta- 

 culocysts, auditory sacs, auditory hairs of marine Crustacea, " ears " 

 of fishes devoid of air-bladders, or, in fact, of any organ whatever, in 

 any aquatic animal, that these organs, unless they be associated 

 with a cavity containing a gas, should serve as auditory organs is 

 simply a physical impossibility. An auditory organ would, moreover, 

 be useless to such an animal as a jelly-fish, and the evolution of such 

 organs in such animals could not be explained by Natural Selection. 

 A real function of some of these organs will be treated of in a 

 future article. 



C. Herbert Hurst. 



2A 



