SELECTION ; BIRDS ; PSYCHOLOGY, COMPARATIVE.) BIBLIOGRAPHY.-C. Darwin, The Descent of Man (1881) ; F. Chap man, Camps and Cruises of an Ornithologist (1909) ; W. P. Pycraft, The Courtship of Animals (1913) ; E. Howard, The British Warblers (1907-14) ; G. M. Levick, Antarctic Penguins (1914) ; J. Meisen heimer, Geschlecht and Geschlechter ( Jena, 1921) • J. S. Huxley, Journ. Linnaean Soc. (Zool.), vol. xxxv. (1923) ; E. Selous, Realities of Bird Life (1927). (J. S. H.)