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When we come to the vertebrates, matters become even more inter-
esting, for it is among them, especially in the birds, that courtship and
display reach their highest elaboration. Only in a few fish is there
much of a courtship, as would be expected from the fact that most
species produce large numbers of eggs which are only fertilized after
laying. The frogs and toads that make night pulse with sound in the
warm regions of the earth use their voices, as do the grasshoppers their
legs or wings, in the interests of reproduction; and if the grasshoppers
were life's first instrumentalists, the frogs were the first vocalists.
The male frog, however, merely broadcasts an advertisement of his
presence; it is among the tailed amphibians that true display is
found. Our common newts in the breeding season take to the water
and develop a high fin all along the back and tail. This is much
larger in the males, who in addition change their winter livery for one
of brighter colours. They may also be seen performing their courtship
—actively moving in front of the females, often scraping up against
them, all the time vibrating the bent tail. The strange fact about this
procedure, however, is that they do not begin their display until
after they have emitted their fertilizing elements. These are deposited
on the bottom of the pond or aquarium inside a special packet of
spcrmatophore, which the female must pick up for fertilization to
occur; and courtship begins when this deposition is completed.
Here we see that display may have a racial function, adjuvant to
successful fertilization, and not an affair between rival males. For
even the most hardened Darwinian would hardly maintain that a
female, if two males simultaneously deposited spermatophorcs and
then began their display before her, would be able to remember which
male had deposited which spermatophore even were she to be better
pleased or more stimulated by the display of one rather than of the
other; and of course unless the approved male were also to be the
father of the young, his pleasing of the female could have no evolu-
tionary effect. No: it seems clear that here the function of display
has again to deal with the "sexual situation" ; with the diilcrence that
it is not merely to advertise the male's presence and masculinity, but
to generate a sexual situation in the mind of the female. As a matter
of fact, Finkler has by experiment shown that in the absence of a
male's display, the female will not pick up spermatophores, so that
this conception of courtship's function being to facilitate fertilization
via the mind, by stimulating the mental mechanism into the right
phase, seems justified.
There is one species of bird for which Darwin's original theory has
been definitely shown to hold good.   That is the well-known shore
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