Independently of the fact of many animals under confinement not coupling, or, if they couple, not producing young, there is evidence of another kind that their sexual functions are disturbed. For many cases have been recorded of the loss by male birds when confined of their characteristic plumage. Thus the common linnet (Linota cannabina) when caged does not acquire the fine crimson colour on its breast, and one of the buntings (Emberiza passerina) loses the black on its head. A Pyrrhula and an Oriolus have been observed to assume the quiet plumage of the hen-bird; and the Falco albidus returned to the dress of an earlier age. (18/65. Yarrell 'British Birds' volume 1 page 506; Bechstein 'Stubenvogel' s. 185; 'Philosoph. Transact.' 1772 page 271. Bronn 'Geschichte der Natur' b. 2 s. 96 has collected a number of cases. For the case of the deer see 'Penny Cyclop.' volume 8 page 350.) Mr. Thompson, the superintendent of the Knowsley menagerie, informed me that he had often observed analogous facts. The horns of a male deer (Cervus canadensis) during the voyage from America were badly developed; but subsequently in Paris perfect horns were produced. When conception takes place under confinement, the young are often born dead, or die soon, or are ill-formed. This frequently occurs in the Zoological Gardens, and, according to Rengger, with native animals confined in Paraguay. The mother's milk often fails. We may also attribute to the disturbance of the sexual functions the frequent occurrence of that monstrous instinct which leads the mother to devour her own offspring,--a mysterious case of perversion, as it at first appears.