Rodents, in the various families, present no uniform uterine construction, there being four kinds corresponding to as many degrees of Mullerian duct fusion and differentiation. The lowest forms simulate the marsupials, another group is like the monotremes, a third shows a complete fusion with a single cordiform uterine body, while the last resembles somewhat the first, but the uterine divisions are bound together and the vagina is divided only half way down. The Insectivora occupy a transitional position resembling higher and lower groups in having a long uterovaginal canal, without distinct cervix, extending upward into long curved cornua. Cetacea (whales) have a highly rugous single vagina, a distinct, short uterine segment divided into two separate horns. The genitalia of Sirenia resemble those of the last group, but the cervix is better developed. In the last three orders the clitoris begins to be well developed and to present externally. Proboscidea have a single vagina separated from the short uterine body by three transverse folds corresponding to the cervix; the two cornua are long and wide. “The foregoing orders present in their uteri all the essential characteristics of uterus bicornis unicollis with single vagina and are therefore the homologues of this anomaly in man.” In the Perissodactyla, the bicornate uterus has a body of a little less than half the whole length; there is a sphincter at the lower end of the body but no projecting cervix. The cornua are longer still in the Artiodactyla and are coiled in a manner suggesting spiral sheep’s horns; there is a differentiated projecting cervix. In cats the length of the uterine body and of the cornua are almost equal and both are flat tubes; the cervix is prominent and the vagina long and rather smooth. The dog’s uterus is similar but the two cornua are bound together or fused before the point at which their termini enter that of the uterine body; the cervix is not very prominent, but well formed and the vagina is rugous. These types correspond to the uterus cordiformis. Lemurs have a common uterovaginal cavity like the Edentata. The lower monkeys possess a long slender uterus with definite superior lateral angles, the last vestiges of the cornua, a prominent cervix and a short rugous vagina. The higher apes have a uterine construction almost identical with that of man at the stage of infantile development. “From the foregoing study it is clearly shown that every anomaly of the female genitalia in Man is in reality the result of atavism and hence, a degenerative change, and inasmuch as every special form of anomaly finds its counterpart in the normal anatomical arrangement of the analogous structures in one or another of the great mammalian groups, one additional item of proof is offered in support of that greatest of biological doctrines, the descent of Man from the lower forms of life.” ANATOMY OF LABOR.