5 1 8 Royal Society. 



rishment, the author states that he has found every structure he has 

 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 processes, 

 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 

 rriolecular, 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. 



