_Birds and mammiferes._--The study of zoology in the Museum of natural history is not confined to the observation of the forms of animals, to the description of their organs; it proposes, besides, to examine their habits, their development, their instinct, and to see if they can be of any use. Formerly, nothing could be learnt of these essential objects but by the relations of travellers. Establishments formed at great expense by princes or rich amateurs to collect and take care of rare animals, were rather objects of luxury and curiosity than an object of study. But since we have had a menagerie at the museum, a new career of observation is open to naturalists. There, animals can be followed in all degrees of their developments, and their manner of living can be compared with their organisation, that anatomy discovers after death; positive knowledge, acquired on the so important phenomena of copulation, gestation, birth; the varieties which depend on age distinguished from those which are produced by climate, nourishment, by crossing races, and the difference determined which really exists between species. If these animals are of a nature to render services to domestic economy or agriculture, and if they breed there are the means to raise and domesticate them, and, so, to procure new resources. The Vigogne, the Lama, the Alpaca, the Tapir, the kanguroo, the Casoar and many others, will pershaps one day be very useful. Considered with relation to science, there are few animals strangers to Europe which are not useful as a study. The history of the greatest part of them is yet very incomplete. That of the lion was not well known until after the lionness of the menagerie had whelps; it is also since two elephants have died ad the menagerie of the museum that an exact knowledge of the anatomy of this great quadruped has been acquired. Travellers cannot be too strongly recommended to neglect nothing in order to send animals to us when they have it in their power to find them living. The small quadrupeds, chiefly those that burrow and hide themselves in the ground are the least known. The bat tribe are still less so, and merit not less the attention and care of travellers. Animals can easily be procured by applying to the natives of the country who know where they are to be found and frequently meet them. They can take them in snares and bring them in alive. It will not be more difficult for them to take in their early youth the quadrupeds whose lurking-places they know, and birds whose nets they have seen.