Marshall presents this subject in the most exhaustive treatise that has appeared for some time. The earlier chapterheads in order are: "The Breeding Season," "The Estrous Cycle in the Mammalia," "The Changes that Occur in the Non-Pregnant Uterus During the Estrous Cycle," "Changes in the Ovary," "Spermatogenesis — Insemination," "Fertilization," "The Accessory Reproductive Organs," "The Biochemistry of the Sexual Organs," and "The Testicle and the Ovary as Organs of Internal Secretion." In this last-named chapter the author makes a most valuable contribution to the literature on the subject. He gives in detail the results of the experimental work of Brown-Séquard, Poehl, Zoth, Pregel, and Bouin and Ancel, Shattock and Seligmann, Boruttau, Ribbert, Carmichael and Marshall, Knauer, Halban, Morris, Glass, Dudley, Essen-Möller, Graefe, Flatau, Kleinhaus and Schenk, Dubreuil and Regaud, Lane-Claypon, Paton, Henderson. Soli, Fichera, Starling and many others. Summing up his fifty pages of review, Marshall says: "The fact that