50 
BULLETIN OF THE BUREAU OF FISHERIES. 
cut. On testing these with sounds before the effects of the cocaine had disappeared 
they were found not to respond to any sounds produced by the pendulum apparatus. 
It therefore seems clear that the relatively slight response that the smooth dogfish 
shows to sounds is mainly dependent upon the ear and that this fish, like Fundulus 
(Parker, 1903), Carassius (Bigelow, 1904), and Cynoscion (Parker, 1910), may be said 
to hear. 
Having ascertained that the smooth dogfish is capable of hearing, I next endeavored 
to determine what part of its ear is concerned with this function. The deep seat of 
this organ and its relatively small size made my task so difficult that I was at last obliged 
to abandon it, but one set of experiments in this direction are not without value. Fol- 
lowing the directions given by Lyon (1900) for cutting cranial nerves, I found that 
the sacculus of the ear of the dogfish was accessible for operative purposes through 
the roof of the mouth and that this organ could be exposed in favorable cases without 
causing bleeding. I made this exposure in seven dogfishes with the intention of opening 
the sacculus and washing out its otolith with a fine current of sea water. In four cases 
the operation was successful on both sides. These four dogfishes were given time 
to recuperate and then were tested. All were strong and vigorous in their swimming 
and, contrary to what would be expected from the statement made by Kreidl (1892), 
they were absolutely indistinguishable from normal individuals in their equilibrium. 
In their reactions to sounds produced by the pendulum apparatus they resembled 
fishes in which the eighth nerves had been cut in that they were responsive only to 
sounds made by a blow of the bob with a momentum of 3 or more. 
Objections might be raised to these results, at least so far as equilibrium is concerned, 
because the animals tested had had both otoliths removed, and in fact Loeb (1891 a) has 
already declared that when only one otolith is taken out the animals show disturbed 
equilibrium in that they swim with the operated side low. I removed a single otolith 
from each of three dogfishes, but though I kept them under observation several days I 
was never able to make out any characteristic irregularity in their equilibrium. These 
results show that the large friable otoliths of the dogfish’s ears, like those of Siredon 
and the frog (Laudenbach, 1899) and Cynoscion (Parker, 1908), are not essential to 
equilibrium, but are, as in the case of Cynoscion at least, concerned with hearing. 
That the ears of the dogfish have to do with equilibrium is so well attested by 
previous investigators that this aspect of the subject calls for no special reconsideration. 
After having had their eighth nerves cut, some smooth dogfishes will acquire the ability 
to swim slowly in normal equilibrium — a condition which, as experiments have shown, 
is certainly in part dependent upon the eye and perhaps in part upon the sense of touch; 
but these animals when made to swim with ordinary rapidity lose equilibrium and pre- 
sent a condition of irregular locomotion such as characterizes the majority of operated 
animals at all times. 
Possibly exceptional cases of this kind influenced Sewell (1884) and Steiner (1886, 
1888) in their opinion that the ear of the dogfish was not concerned with equilibrium — an 
opinion that has been set at naught by the more recent work of Loeb (1891 b), Kreidl 
(1892), Lee (1892, 1893, 1894, 1898), Bethe (1899), Gaglio (1902), and Quix (1903). 
