The present exhibit is more complete than that of the other departments of the museum. Of birds there is a large mounted series, one of the finest in existence, but it is so indifferently housed that it fails to make the impression it should. Of mammals there is a good North American series, and there are some excellent examples of exotic species. There is a good and rather large exhibit of the various groups of the lower forms of animals, including an especially fine series of corals and sponges. These are the only series at present exhibited which can be considered at all comprehensive. Of the great groups of fishes, reptiles, and amphibians there is room only for an outline representation. The wonderful variety of form among insects can be scarcely more than suggested in the space available. Of plants there has hitherto been no exhibit worthy of the name, and the space which it has now been possible to set aside is entirely out of proportion to the vast extent and importance of this great kingdom of Nature. Every natural-history museum of the first class should have at least two comprehensive exhibition series. The first, the _Systematic Series_, is a series representing the natural groups, among which all animals and plants, from the highest to the lowest, are divided. The second, the _Faunal and Floral Series_, is a series showing the animals and plants characteristic of each of the grand divisions of the earth's surface, which naturalists have established as a result of their study of these two kingdoms of Nature. These two great comprehensive exhibits should be supplemented by a number of _Special Series_, illustrating the more interesting phenomena and phases of life, such as the macroscopic and microscopic structure of animals and plants and their development from the germ to the fully adult individual, and special modifications of form and color by which animals are protected from their enemies; the adaptations for peculiar environments and modes of life; the characteristics of youth, maturity, and old age; the variation in form, size, and color among individuals of the same species; the domiciles and other works constructed by birds, mammals, insects, and the like. To these series should be added another of great importance, the _Economic Series_, representing the animals and plants as related to the activities and needs of man. Any one of these principal series in its full development would more than fill the entire space now available. 3. There should be developed a museum of practical geology in the broadest sense, which will be of service to every producer and consumer of American mineral products, and to all students of geology who are engaged in either economic or purely scientific investigations.