nguished, but in many cases they bear no resemblance
in any single characteristic. What could be more unlike than the songs
of the Willow-Warbler and of the Chiffchaff, of the Marsh-Warbler and
the Reed-Warbler, or of the Yellow Bunting and the Cirl Bunting?

Now when different individuals collect in flocks at certain seasons,
they assist one another in finding food, and afford mutual protection by
giving timely warning of the approach of a common enemy, and the
gregarious instinct is thus of great advantage to the species; but no
matter how powerful the impulse to flock might be, if there were no
adequate means of communication, the different units would frequently
fail to discover their neighbours. Here the specific cries and calls
come into play, enabling them as they move about in search of food, or
change their feeding grounds, or whilst they are on migration, to keep
constantly in touch with one another; and hence one purpose that these
call-notes serve is that of recognition. Moreover, they convey their
meaning to individuals of other species and are acted upon, and are thus
in every sense socially serviceable; but on the other hand, whilst
there is much evidence to show that the song is of great individual
value, there is none to show that it is in any like manner of direct
advantage to the community.

If, then, there is in the call-notes an adequate means of communication
and of recognition, why do I suggest that the song has also been evolved
primarily for the purpose of recognition?

What, first of all, are the conditions in the life behaviour during the
season of reproduction that make the intervention of the voice a
consideration of such importance? The general result of our
investigation might be summed up thus: we found that the male inherits a
disposition to secure a territory, that at the proper season this
disposition comes into functional activity and leads to its
establishment in a definite place, and that it cannot search for a mate
because its freedom of action in this respect is forbidden by law; that
the female inherits no such disposition, that she is free to move from
place to place, free to satisfy her predominant inclination, and to seek
a mate where she wills; and, since the appropriate organic condition
which leads to pairing must coincide with appropriate conditions in the
environment, that the union of the sexes must be accomplished without
undue delay. Furthermore we found that a terri