HEARING AND ALLIED SENSES IN FISHES. 
49 
that something more might he attained in this direction, and I therefore resolved to 
give particular attention to the reactions of a few fishes with the view of ascertaining 
whether or not they showed any evidence of hearing. 
At the outset I thought it best to experiment on some common sound-producing 
species, and for this purpose I did some preliminary work on the swell-fish ( Ckilo - 
mycterus schoepft), the squeteague ( Cynoscion regalis), and the sea robin ( Prionoius 
carolinus) . To all of these, practical objections were found, and I was at. last obliged 
to abandon them for fishes that produce no sounds. Among these, three species 
were found to be especial ly sensitive to slight vibrations — the king-fish ( Menticirrhus 
saxatilis), and the two common species of killi-fish ( Fundulus majalis and F. hetero- 
clitus). Because of the great abundance of F. heteroclitus, the ease wil l: which it 
could be operated upon, and its great hardiness, I chose it for study, and the observa- 
tions recorded on the following pages, unless otherwise stated, refer to this species. 
The ears in Fundulus heteroclitus. — When a tank containing a number of Fun- 
dulus heteroclitus is struck with the open hand so that the fish can not see the 
movement of striking, they respond to the vibrations by springing suddenly an inch 
or so through the water. The question to be considered is whether these vibrations 
stimulate the fishes through the skin, the lateral-line organs, the ears, or some 
combination of these. If it could be shown that the ears were not stimulated by 
the vibrations, it seems to me that we would have evidence pointing to the conclusion 
that the fishes did not hear. If on the other hand it could be demonstrated that the 
vibrations did stimulate the ears, the evidence would lie conclusive that the animals 
possessed the sense of hearing. To test these points considerable experimentation 
was necessary. 
Much of the work that has been carried out heretofore has been done with 
sound generated in air but intended to affect fishes in water. That this method is 
extremely inefficient I found by trying the following experiment. If a dinner bell 
is rung in the air by a person standing breast-deep in water, it will, of course, be 
heard easily by a second person standing in a similar way a yard or two off. If, 
however, the second person puts his head under the water during the ringing of the 
bell the sound seems to cease almost entirely and is not again heard clearly by the 
diver till he emerges. In like manner a bell rung or hit with a stone under water 
is heard, at best, very faintly by a person standing in the water unless his head is 
under the surface. In other words, the plane separating air and water is, under 
ordinary circumstances, an almost impenetrable one for most sounds, whether they 
are generated on one side or the other of it, and many of the negative results 
obtained by previous investigators on the sense of hearing in fishes may have been 
due not so much to the absence of hearing in the animals experimented upon as to 
their inaccessibility to the sound, or at least to sound of an intensity sufficient to 
stimulate. This difficulty has been recognized by Kreidl, and in devising apparatus 
I have profited by his experience and used sound-producing appliances that were 
in direct contact with the water containing the fishes. 
The chief piece of apparatus that I used consisted of an ordinary marine 
aquarium (pi. 9, fig. 1) with a slate base, two heavy glass sides, and originally two slate 
ends, one of which, however, I replaced by a piece of deal board free from knots, to 
serve as a sounding-board. The inside dimensions of the aquarium were as follows: 
depth, 40 cm. (16 in.); breadth, 37 cm. (15 in.); and length, 87 cm. (35 in.). To the 
middle of one edge of the sounding-board a stout beam of wood was attached 
F. C. B. 1902—4 
