Mr. Wallace entirely agreed with all the main principles advocated by Dr. Sclater, such as the separate government of the Natural History Museum, the association of Palæontology with Zoology, and the separation of the collections into a "typical and a scientific series," both of which should be at all times available; but he differed from him on a point which he considered to be no less important than any of these, viz., as to the mode of arrangement of the specimens which would be most efficient for all the purposes such a museum should fulfil. In a national institution, if any part of it was set apart for the elevation, instruction, and amusement of the public, these purposes should be carried out in the most efficient manner, and this could not be done by the system of wall-cases advocated by Dr. Sclater, and which he (Mr. Wallace) believed to be radically wrong. The objections to these wall-cases were numerous:--

    1. They admit of any object being seen by the smallest number of persons at once, so that any one person studying an object, almost necessarily monopolises it, and prevents others from approaching it, an inconvenience that reaches its maximum in the recessed cases exhibited in Dr. Sclater's plan.

    2. Objects in wall-cases can be seen only on one side, which, as all sides of natural objects require to be seen, would necessitate many specimens to do the duty of one.

    3. The observer on the one side, from which alone he can see an object, will generally stand in his own light, and will often have distinct vision further impaired by reflection from the glass.

    4. When small objects occur alternately with large ones, a great waste of space occurs, and the attention is distracted from the less conspicuous object.

    5. The use of wall-cases on one side of a gallery for an entire museum, is an expensive and wasteful mode of arrangement.

    Objections (1) (2) and (3) are of the greatest importance. A public national museum must accommodate the thousands who throng to it on holidays, when alone the working classes can reap its benefits; and they should be invited and induced to examine and study, not merely to gaze and pass on. Teachers and parents should be able to give information as to the groups exhibited without interfering with other visitors, none of which things are possible with a range of wall-cases. The system advocated by Mr. Wallace was that of detached cases on tables or on the floor, of various sizes, and each exhibiting one typical object or group of objects, capable of being seen on all sides, and admitting of convenient examination in the best light by the greatest number of persons at once. The system had been adopted in a new museum at the India House, and at South Kensington, and was advocated by Dr. Gray, and partially exemplified in the great gorilla case, the groups of birds of paradise, and other detached cases in the British Museum. The numerous and very great advantages of this system should not be lost for the sake of an infinitesimal increase of convenience to scientific men. The great majority of specimens exhibited in the public galleries would consist of common species, of which an ample series of specimens would be preserved in the scientific collection for study. Of the few rare species which it might be advisable to exhibit to the public, perhaps not more than one a week would be required for scientific examination, and all such might be so mounted as to be easily brought into the students' room, adjacent to the gallery, when required. The man of science would thus lose nothing, while the public would gain incalculably; and so greatly was Mr. Wallace impressed with the educational superiority of one mode of arrangement over the other, that he believed it would be better to have the very rare and unique species represented by drawings or models only in the public department, rather than have the whole collection arranged in wall-cases, for the one purpose of allowing the scientific man to get them out more easily on the rare occasions when he required them.