Animals in a state of nature usually appear to seek seclusion for sexual intercourse, although this instinct is lost under domestication. Even the lowest savages, also, if uncorrupted by civilized influences, seek the solitude of the forest or the protection of their huts for the same purpose; the rare cases in which coitus is public seem usually to involve a ceremonial or social observance, rather than mere personal gratification. At Loango, for instance, it would be highly improper to have intercourse in an exposed spot; it must only be performed inside the hut, with closed doors, at night, when no one is present.[13] It is on the sexual factor of modesty, existing in a well-marked form even among animals, that coquetry is founded. I am glad to find myself on this point in agreement with Professor Groos, who, in his elaborate study of the play-instinct, has reached the same conclusion. So far from being the mere heartless play by which a woman shows her power over a man, Groos points out that coquetry possesses "high biological and psychological significance," being rooted in the antagonism between the sexual instinct and inborn modesty. He refers to the roe, who runs away from the stag--but in a circle. (Groos, _Die Spiele der Menschen_, 1899, p. 339; also the same author's _Die Spiele der Thiere_, pp. 288 _et seq._) Another example of coquetry is furnished by the female kingfisher (_Alcedo ispida_), which will spend all the morning in teasing and flying away from the male, but is careful constantly to look back, and never to let him out of her sight. (Many examples are given by Büchner, in _Liebe und Liebesleben in der Tierwelt_.) Robert Müller (_Sexualbiologie_, p. 302) emphasizes the importance of coquetry as a lure to the male. "It is quite true," a lady writes to me in a private letter, "that 'coquetry is a poor thing,' and that every milkmaid can assume it, but a woman uses it principally in self-defence, while she is finding out what the man himself is like." This is in accordance with the remark of Marro, that modesty enables a woman "to put lovers to the test, in order to select him who is best able to serve the natural ends of love." It is doubtless the necessity for this probationary period, as a test of masculine qualities, which usually leads a woman to repel instinctively a too hasty and impatient suitor, for, as Arthur Macdonald remarks, "It seems to be instinctive in young women to reject the impetuous lover, without the least consideration of his character, ability, and fitness."