Descent of Man, second edition, p. 567. Groos, in his discussion of music, also expresses doubt whether hearing plays a considerable part in the courtship of mammals, Spiele der Menschen, p. 22.
Féré, L'Instinct Sexuel, second edition, p. 137.
See Biérent, La Puberté Chapter IV; also Havelock Ellis, Man and Woman, fourth edition, pp. 270-272. Endriss (Die Bisherigen Beobachtungen von Physiologischen und Pathologischen Beziehungen der oberen Luftwege zu den Sexualorganen, Teil III) brings together various observations on the normal and abnormal relations of the larynx to the sexual sphere.