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March 15th, 1846. — A paper by the Secretary, John Quekett, Esq. "On the intimate structure of bone in the four great classes of Ani- mals, viz. Mammals, Birds, Reptiles, and Fishes, with some remarks on the great value of the knowledge of such structure in classifying minute fragments of fossil organic remains," was read. After allud- ing to the highly important results obtained by Mr. Owen, by the aid of the microscope in determining the affinities of extinct animals, by means of their teeth, the author went on to state, that having for some time paid considerable attention to the structure of bone in the fbur great classes of animals, he had found certain characters peculiar to each great class by which a bone of one class could be distinguish- ed from that of another. He then briefly described certain characters which were present in all bones, and then those which were peculiar to each class, viz. the Haversian canals and the bone cells, with their little tubes (canaliculi) proceeding from them, and he applied the cha- racters derived from the bone cells to the determination of the class of animals to which any minute fragments may have belonged ; for he had ascertained that the bone cells were smallest in birds, a little lar- ger in Mammalia, and largest of all in the Reptilia ; the bone cells of fishes were remarkable for their being so unlike either of the three preceding classes, that having been once seen, they could not easily be mistaken. The author then noticed the relative proportions of the bone cells and blood corpuscles of the same animal, and concluded by remarking, that however different the size of animals of the same class may be, the bone cells did not vary according to the difference in size : thus the mighty Iguanodon, some scores of feet in length, had no larger bone cells than the lowliest lizard which we trampled under our feet, nor the horse, or the ox, than the smallest of our quadrupeds, the mouse.

April 15th. Esq., F.R.S., in the Chair. — A paper entitled "Observations on the Structure and Nature of the Fi- laria Medinensis, or Guinea Worm," by G. Busk, Esq. was read. The author, before entering upon the account of the anatomical struc- ture of the guinea worm, premised a short statement of what is known with regard to its habits, and the localities in which it occurs endemi- cally. This was done in order to afford an opportunity of drawing probable conclusions as to the nature of the parasite, from considera- tion of its habits, as well as of its structure. It was mentioned that the Filaria Medinensis is very limited in its range of distribution, occur-