ABSTRACT It has always been to us a matter of some surprise as well as regret that the authorities having the direction of great public museums in this country have hitherto taken no steps in the direction of exhibiting to the numerous persons seeking instruction and amusement in such places that vast field of life and structure which is opened out by the microscope. It is no less strange than true, that not only is our national collection destitute of the means necessary for rendering the public conversant with the minuter forms of life, and the details of form in the higher animals, but even to the student no facilities whatever are afforded in the domain of microscopic research by that institution. It would be deemed probable by most persons that in a museum, one of whose chief directors has obtained great reputation as an odontologist, there should have been a collection of sections of various recent and fossil teeth, adapted for examination with the microscope, and arranged for comparison, not to speak of the series of wellmounted insects, Annelids, and other smaller and almost invisible animals, that might have been looked for in the zoological department. But this is not the case ; neither is there a collection of microscope-sections of teeth, nor any series of specimens mounted for use with that instrument. The student of comparative histology and minute zoology and botany would be left entirely to his own resources and those of his private friends, were it not for the existence of two collections in London to which he can gain access, and which, however incomplete, when we consider what a public collection of microscopic preparations ought to be, are nevertheless eminently useful and interesting, and tend far to supply the deficiency which we have noticed elsewhere.