Page:Proceedings of the Royal Society of London Vol 4.djvu/309

Rh by Von Baer. Farther, that the origin of the " laminae dorsales " of this naturalist (the " central nervous system" of Reichert) is not simultaneous with, but anterior to, that of the chorda.

The author then reviews the observations of Rathke and Reichert on the chorda dorsalis, which contain internal evidence, he thinks, of a process in the development of Fishes, Reptiles, and Birds, the same as that which he has observed in Mammalia ; namely, the ori- gin of the embryo out of the nucleus of a cell.

And it is his opinion that this obser^'ation may assist to solve a question on which physiologists are not agreed ; for it shows, that if the nucleus of a cell is a single object, the first rudiments of the embryo are not two halves. The author thinks that unless the very earliest periods are investigated, it is in vain that we attempt to learn what that is, of which the rudiments of the embryo are com- posed. From not attending to this, physiologists have supposed their " primitive trace" to arise in the substance of a membrane, which the author, in liis second series on the embryo, showed could not be the case. To the same cause he thinks is referable an opinion re- cently advanced by Reichert, that the first traces of the new being are derived from cells of the yelk.

Charles Enderby, Esq. and James Cosmo Melvill, Esq. were bal- loted for and duly elected into the Society.

A paper was read, entitled, " On the Corpuscles of the Blood." Part II. By Martin Barry, M.D., F.R.S.S. L. and E.

The observations recorded in this memoir are founded on an ex- amination of the blood in every class of vertebrated animals, in some of the Invertebrata, and in the embryo of Mammalia and Birds. The nucleus of the blood-corpuscle, usually considered as a single object, is here represented as composed, in some instances, of two, three, or even many parts ; these parts having a constant and determinate form. In the substance surrounding the nucleus, the author has frequently been able to discern, not merely " red colouring matter," but cell-like objects ; and he points out an orifice as existing at certain periods in the delicate membrane by which this substance is surrounded. In a former memoir he had differed no less from previous observers regarding " cells." He had sho^ni, for instance, that the nucleus of the cell, instead of being " cast off as useless, and absorbed," is a centre for the origin, not only of the transitory contents of its own cell, but also of the two or three principal and last-formed cells, destined to succeed that ceil; and that a separation of the nucleus into two or three parts, is not, as Dr. Henle had supposed in the case of the Pus and Mucus-globule (the only instances