Dr Barry's Besearches in Embryology, 89 



The existing view, namely, that a nucleus, when it leaves 

 the membrane of its cell, simply disappears by liquefaction, is 

 inapplicable to any nucleus observed in the course of these in- 

 vestigations. The nucleus resolves itself into incipient cells in 

 the manner above described. In tracing this process, it ap- 

 pears that the nucleus, and especially its central pellucid ca- 

 vity, is the seat of changes which were not to have been ex- 

 pected from the recently advanced doctrine, that the disappear- 

 ing nucleus has performed its entire ofl&ce by giving origin at 

 its surface to the membrane of a single cell. It is the myste- 

 rious centre of a nucleus which is the point of fecundation ; 

 and the place of origin of two cells constituting the foundation 

 of the new being. The germinal vesicle, as already stated, is 

 the parent cell, which, having given origin to two cells, disap- 

 pears, each of its successors giving origin to other two, and so 

 on. Perpetuation, however, at this period, consists, not merely 

 in the origin of cells in cells, but in the origin of cells in the 

 pellucid central part of what had been the nucleus of cells. 



The author shews that neither the germinal vesicle, nor the 

 pellucid object in the epithelium, is a cytoblast. He suggests, 

 that the cells into which, according to his observations, the 

 nucleus becomes resolved, may enter into the formation of se- 

 condary deposits, for instance, spiral fibres ; and that they 

 may contribute to the thickening which takes place, in some 

 instances, in the cell-membrane. 



The germ of certain plants passes through states so much 

 resembling those occurring in the germ of mammiferous ani- 

 mals, that it is not easy to consider them as resulting either 

 from a different fundamental form, or from a process of deve- 

 lopment which, even iiQ its details, is not the same as what has 

 been above described ; the fundamental form in question in 

 Mammalia, and, therefore, it may be presumed, of Man him- 

 self — being that which is permanent in the simplest plants — the 

 single isolated cell. 



