cases, exclusive purpose appears to be either to call or charm the
opposite sex.
The sounds produced by fishes are said in some cases to be made only by
the males during the breeding-season. All the air-breathing Vertebrata
necessarily possess an apparatus for inhaling and expelling air, with a
pipe capable of being closed at one end. Hence when the primeval
members of this class were strongly excited and their muscles violently
contracted, purposeless sounds would almost certainly have been
produced; and these, if they proved in any way serviceable, might
readily have been modified or intensified by the preservation of
properly adapted variations. The lowest Vertebrates which breathe air
are Amphibians; and of these, frogs and toads possess vocal organs,
which are incessantly used during the breeding-season, and which are
often more highly developed in the male than in the female. The male
alone of the tortoise utters a noise, and this only during the season
of love. Male alligators roar or bellow during the same season. Every
one knows how much birds use their vocal organs as a means of
courtship; and some species likewise perform what may be called
instrumental music.
In the class of Mammals, with which we are here more particularly
concerned, the males of almost all the species use their voices during
the breeding-season much more than at any other time; and some are
absolutely mute excepting at this season. With other species both
sexes, or only the females, use their voices as a love-call.
Considering these facts, and that the vocal organs of some quadrupeds
are much more largely developed in the male than in the female, either
permanently or temporarily during the breeding-season; and considering
that in most of the lower classes the sounds produced by the males,
serve not only to call but to excite or allure the female, it is a
surprising fact that we have not as yet any good evidence that these
organs are used by male mammals to charm the females. The American
Mycetes caraya perhaps forms an exception, as does the Hylobates
agilis, an ape allied to man. This gibbon has an extremely loud but
musical voice. Mr. Waterhouse states (30. Given in W.C.L. Martin s
General Introduction to Natural History of Mamm. Animals, 1841, p.
432; Owen, Anatomy of Vertebrates, vol. iii, p. 600.), It appeared
to me that in ascending and descending the scale, the intervals were
always exactly half-tones; and I am sure that the highest note was the
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