examined to arise out of corpuscles having the same appearance as the corpuscles of the blood. The following are the tissues which he has submitted to actual observation, and which have given the above result, namely, the cellular, the nervous, and the muscular ; besides cartilage, the coats of blood-vessels, several membranes, the tables and cells of the epithelium, the pigmentum nigrum, the ciliary pro- cesses, the crystalline lens itself, and even the spermatozoon and the ovum.
The author then traces the nucleus of the blood- corpuscle into the pus-globule ; showing that every stage in the transition presents a definite figure. The formation of the pus- globule out of the nucleus of the blood-corpuscle is referable to the same process, essentially, as that by means of which the germinal spot comes to fill the germinal vesicle in the ovum. This process, which, in a former memoir, he had traced in the corpuscles of the blood, he now shows to be uni- versal, and nowhere more obvious than in the reproduction of the tables of the epithelium. The epithelium-cylinder seems to be con- stituted, not by coalescence of two objects previously single, as has been supposed, but by division of a previously single object. Certain objects, called by the author primitive discs, exhibit an inherent con- tractile power, both when isolated, and when forming parts of a larger object; an incipient epithelium-cylinder having been observed by him to revolve by this means. Molecular motions are sometimes discernible within corpuscles of the blood. The author has no- ticed young blood-corpuscles exhibiting motions, comparable to the molecular, and moving through a considerable space ; and he has met with the nuclei of blood-corpuscles endowed with cilia, revol- ving, and performing locomotion. In his first paper on the Corpuscles of the Blood, he described certain instantaneous changes in form which he had observed in blood- corpuscles, and afterwards expressed his belief, that these changes were referable to contiguous cilia, although he had not been able to discern any such cilia. He now states that subsequent observation inclines him to think that these changes in form arise from some inherent power, distinct from the motions occasioned by cilia. The primitive disc, just mentioned, seems to correspond, in some instances, with the " cytoblast" of Schleiden. Thus the very young corpuscle of the blood is a mere disc ; but the older corpuscle is a cell. The author minutely de- scribes the mode of origin of the pigmentum nigrum ; showing that it arises in a similar manner in the tail of the tadpole, and in the choroid coat of the eye. He had before described the Graafian vesicle as formed by the addition of a covering to the previously- existing ovisac : this covering, he afterwards stated, becomes the corpus luteum. He now confirms these observations, with the addition, that it is the blood-corpuscles entering into the formation of the covering of the ovisac, which give origin to the corpus luteum. The spermatozoon appears to be composed of a few coalesced discs. The fibres of the crystalline lens are not elongated cells, as supposed by Schwann ; but coalesced cells, at first arranged in the same man- ner as beads in a necklace.
