Generation of the Pouch-Animals.—Mexico and expecially Brazil produce, as it is known, several varieties of the Marsupial Mammifers, all the family of the Didelphides, but some, such as the Didelphes, provided with a true pouch, other, such as the Micoures and the Hermiures, without pouch properly so called, doubtless it will be possible to procure live specimens of both sexes. We cannot too strongly urge the naturalist to neglect nothing to clear up the mystery, yet but partially penetrated, of the manner these mammifers reproduce kind. We are far indeed, from the period, when it was believed that the animals were formed at the dugs of their dams. The labors of Hunter, Home, Geoffroy Saint-Hilaire de Blainville and other observers, have long since removed from science this inadmissible anomaly; some years ago, M. Owen, having the fortunate opportunity of examining the uterus of a female Kanguroo, that died in bringing forth, and of dissecting the embryo it contained has developped several facts of great interest.
But the intra-uterine gestation of the marsupials, and the second singular gestation peculiar to them, still remain new and important subjects of study for anatomy and comparative physiology. Animals or parts of animals sent in alcohol from America, the Indian Archipelago, or New-Holland, some cases of reproduction occuring in Paris and London, such are the imperfect elements which the French and English physiologists possess; their efforts to procure a certain number of specimens have always been unsuccessful. This determined Geoffroy Saint-Hilaire to draw up in 1824, and the administration of the museum to send to all the countries where the Marsupials are found, detailed information on the state of the question at that time, and of the researches imperiously required by the wants of science from observers in those regions.
1o If learned naturalists could send a series, so that the evolution of the ovula, the embryo, and the egg could be studied from its fecundation to its discharge from the uterus, they would thus supply Zootomists with all the elements of the great work we have just pointed out.
2o To observe with care the circumstances of the passage of the fœtus to the vagina of the pouch.
3o To describe in the most accurate manner the way the fœtus clings to the teat. They should determine this by observations of several specimens of different ages, and repeat, if possible, on the Didelphides, the curious experiments made by Collie and Morgan on the mammary fœtus of a Marsurpial of an entirely different family.
4o To determine exactly and analyse the liquids contained in the breasts of the dam, and the digestive organs of the mammary fœtus.
5o To examine in the living subjects the remarkable arrangement of the respiratory organs, discovered by Geoffroy Saint-Hilaire, which establish a connexion between the posterior nostrils and the cavity of the larynx.
We are entirely without notions concerning the abdominal folds, which, in this kind, take the place of the pouch, in a certain degree, and know nothing of the modifications these folds pass through in the different epochs of gestation.
Anthropology.—The countries to which these instructions are adressed to are doubtless among those where naturalists can collect the greatest number of interesting facts for this branch of natural history, formerly neglected and to which has been given, for some years past, an impulse worthy of its high importance. In Mexico and in the United States three of the principal human races are found together; the race peculiar to America, the Caucasian race from different countries of Europe, and the Ethiopian carried over in its train. All these races cross-breed, and from the crossing of the half-breeds with them and each other, result many curious combinations, whose scientific study is of the highest interest.