[41] A similar condition has been noted among butterflies, where, in some cases, differences in the colouring of the wings on two sides has been found to correspond to an internal co-existence of the male and female sex-organs. It seems probable that this interesting phenomenon of abnormal hermaphroditism is of much commoner occurrence than the cases that have been recorded (_Evolution of Sex_, p. 67). [42] "The Love of Slugs," article by James Bladon, _Zoologist_, Vol. XV., 1857, p. 6272. [43] "Molluscs," article by Rev. L.H. Cooke, _Cambridge Natural History_, Vol. III. p. 143. Both these cases are quoted by Havelock Ellis in his illuminative "Analysis of the Sexual Impulse," the opening chapters in the third volume of the _Studies in the Psychology of Sex_. [44] Trout also fight during the breeding season. _Chapters on Human Love_, by Geoffrey Mortimer (W.M. Gallichan), pp. 13-14. [45] _Evolution of Sex_, pp. 625-626. _Chapters on Human Love_, p. 14. [46] _Problems of Sex_, by J.A. Thomson and Prof. Patrick Geddes, p. 20. [47] _Evolution of Sex_, pp. 270-272, 295. [48] _Natural Science_, Nov. 1894, quoted by Havelock Ellis, _Psychology of Sex_, Vol. III. p. 30. [49] _Evolution of Sex_, p. 265. CONTENTS OF CHAPTER V COURTSHIP, MARRIAGE AND THE FAMILY I.--_Among the Birds and Mammals_ Courtship and marriage among birds and mammals--Every form of association similar to human marriage--A high standard of love-morality among birds--Monogamy, polygamy, and polyandry--Cases of absolute profligate promiscuity--Suggestions of all the sexual sins of humanity--The phenomena of courtship--The law of battle--Battles of mammals and male gallinaceae--The frenzy of love--Where supremacy in love is gained by force the males become stronger and better armed than the females--Importance of this--Gentler ways of wooing--AEsthetic seductions--Courteous duels--The note of joy in love among birds--Affectionate partnerships lasting for life--Frequency of monogamy among birds--Co-operation of both sexes in forming the home and caring for the young--The amatory dances of birds--Significance of dancing--Numerous illustrations--The use of song and decorative plumage--Musical seduction--AEsthetic constructions--The extraordinary power of sex-hunger--General propositions. II.--_Further Examples of Courtship, Marriage and the Family among Birds_