1893. BIOLOGICAL THEORIES. 353 
intensity of a sound (whatever 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. HerBeErT Hurst. 
2A 
