We may perhaps connect this with an observation of E.Selous (_Zooelogist_, May and Sept., 1901) on a bird, the Great Crested Grebe; after pairing, the male would crouch to the female, who played his part to him; the same thing is found among pigeons.

Selous suggests that this is a relic of primitive hermaphroditism.

But it may be remembered that in the male generally sexual intercourse tends to be more exhausting than in the female; this fact would favor a reversion of their respective parts.
[8] E.Selous, "Sexual Selection in Birds," _Zooelogist_, Feb., 1907, p.
65; ib., May, p.169.Sexual aberrations generally are not uncommon among birds; see, e.g., A.Heim, "Sexuelle Verirrungen bei Voegeln in den Tropen," _Sexual-Probleme_, April, 1913.
[9] See Moll, _Untersuchungen ueber die Libido Sexualis_, 1898, Bd.

i, pp.
369, 374-5.

For a summary of facts concerning homosexuality in animals see F.Karsch, "Paederastie und Tribadie bei den Tieren auf Grund der Literatur," _Jahrbuch fuer sexuelle Zwischenstufen_, Bd.