The Coyness of birds is illustrated by the following cases cited by Büchner from Brehm and A. and K. Müller: “A genuine coquette is the female cuckoo, who answers the call of the male with a peculiar resonant, tittering or laughing love-call. ‘The call is seducing, promising in advance, and its effect on the male simply enchanting.’ But how long the lovers pursuing the siren have to wait before she accepts one of them! A wild flight begins, among bushes and tree-tops, while the female encourages the pursuers with repeated calls, and finally gets them into a state of erotic excitement bordering on madness. At the same time the female is no less excited than her frantic suitors. Her favourite, no doubt, is the most eager of the lovers, and her apparent resistance simply the desire to excite him still more!... The female of the icebird (_Alcedo ispida_) often teases her lover half a day at a time, by repeatedly approaching him, screaming at him, and flying away again. At the same time she never loses sight of him, but in her flight casts glances at him backwards and sidewise, moderates the rapidity of her flight, and returns in a wide curve if the male suddenly ceases from his pursuit.” Could anything be more naïvely, more humanly, more exquisitely feminine? If a lover, says a French philosopher, fails in his suit, let him desist for a moment, and she will presently call him back. No inquiry has ever been made by naturalists, so far as I am aware, as to the origin of Coyness among animals. Two probable sources of this feeling may therefore be here suggested. The first is a vague instinctive presentiment (based on inherited cerebral impressions) that with mating the labours of life will begin: the painful laying of eggs; the loss of liberty during incubation—an incalculable loss to these most active of all animals; and the care of the young, which, again, is not a trifling matter, inasmuch as a family of starlings, for example, needs for its daily food more than eight hundred snails, caterpillars, etc.; and birds sometimes perish from exhaustion in the attempt to feed their offspring. The second source of Coyness is probably another instinctive feeling (based on inherited experience) which induces the female to defer her choice until the combats and manœuvres of the males have shown which one is the most energetic, courageous, and persistent: for he will obviously be best able to support her brood, and protect it as well as herself against enemies. Hence, during the combats of rival males, the female is commonly a passive spectator, and at the end quietly marches or flies off with the victor. All of which, by the way, shows that among animals already masculine love is deeper than feminine. Indirectly, it is true, feminine Coyness is the cause of Love—but only of _masculine_ Love; for if the female animal always accepted the first male who asked her—