muscles attached to the swim bladder, which serves as a resounding
board and by the vibration of the intrinsic muscles of the swim
bladder. By this latter means the Trigla produces pure and long-drawn
sounds which range over nearly an octave. But the most interesting case
for us is that of two species of Ophidium, in which the males alone are
provided with a sound-producing apparatus, consisting of small movable
bones, with proper muscles, in connection with the swim bladder. (41.
Comptes-Rendus, tom. xlvi. 1858, p. 353; tom. xlvii. 1858, p. 916;
tom. liv. 1862, p. 393. The noise made by the Umbrinas (Sciaena
aquila), is said by some authors to be more like that of a flute or
organ, than drumming: Dr. Zouteveen, in the Dutch translation of this
work (vol. ii. p. 36), gives some further particulars on the sounds
made by fishes.) The drumming of the Umbrinas in the European seas is
said to be audible from a depth of twenty fathoms; and the fishermen of
Rochelle assert that the males alone make the noise during the
spawning-time; and that it is possible by imitating it, to take them
without bait. (42. The Rev. C. Kingsley, in Nature, May 1870, p.
40.) From this statement, and more especially from the case of
Ophidium, it is almost certain that in this, the lowest class of the
Vertebrata, as with so many insects and spiders, sound-producing
instruments have, at least in some cases, been developed through sexual
selection, as a means for bringing the sexes together.
AMPHIBIANS.
URODELA.
[Fig. 32. Triton cristatus (half natural size, from Bell s British
Reptiles ). Upper figure, male during the breeding season; lower
figure, female.]
I will begin with the tailed amphibians. The sexes of salamanders or
newts often differ much both in colour and structure. In some species
prehensile claws are developed on the fore-legs of the males during the
breeding-season: and at this season in the male Triton palmipes the
hind-feet are provided with a swimming-web, which is almost completely
absorbed during the winter; so that their feet then resemble those of
the female. (43. Bell, History of British Reptiles, 2nd ed., 1849,
pp. 156-159.) This structure no doubt aids the male in his eager search
and pursuit of the female. Whilst courting her he rapidly vibrates the
end of his tail. With our common newts (Triton punctatus and cristatus)
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