548 
DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
the interior of each of the larger objects in the germinal vesicle Plate XXIII. fig. 169. c, 
presented an appearance fully warranting the section fig. 177 ; though it was not pos- 
sible to represent this appearance in that small figure. The section fig. 177- is, in 
fact, a delineation of one of the objects in the substance surrounding the germinal 
vesicle in an ovarian ovum of 8^ hours. And in no object of the kind sufficiently 
advanced, and the interior of which the eye could reach, have I failed to find traces 
of a structure essentially the same (see Plate XXV. figs. 200. 201.). 
383. Only a first and second order of discs or incipient cells have been exhibited 
in that section (Plate XXIII. fig. 1 77-)s because I wish to figure nothing more than 
has been actually seen. But my experience of these objects is such as to warrant the 
belief that more orders might have been introduced. Indeed it is not possible to say 
where the process ends, except in liquefaction. 
384. In following out this process we have thus seen the nucleus, and especially its 
centre, to be the seat of changes which were not. to have been expected from the ex- 
isting doctrine, that the disappearing nucleus has performed its entire office by giving 
origin at its surface to the membrane of a single cell. It is the mysterious centre of 
a nucleus — the germinal spot — which is the point of fecundation, and the place of 
origin of two cells constituting the foundation of the new being. The germinal vesi- 
cle is the parent cell, which, having given origin to two cells, disappears, 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 as we have seen, in the 
origin of cells in the pellucid centres of the nuclei of cells'!'. 
385. The quotations in the Appendix I think will be found to contain internal evi- 
dence of Schleiden having seen the nucleus undergoing changes such as those above 
described ; but he was far from recognizing them. This author states that the nuclei 
— or, as he calls them, the “cytoblasts” — “grow and diminish in their size.” He 
found his nucleolus to present various appearances. In well-developed “cytoblasts” 
it resembled “ a thick ring or a thick-walled hollow globule in those less developed, 
there was seen “ only the outer sharp contour of this ring, and in its middle an opake 
point;” in “cytoblasts” still smaller, “only a sharply circumscribed spot;” in others, 
no more than “a remarkable, minute, opake point;” and in the smallest and most 
transitory, “ it was not to be detected.” He observed the diameter of the nucleolus 
to vary “from half that of the cytoblast to points immeasurably small.” Sometimes 
the nucleolus appeared to him to be “ more opake, at others more pellucid than the 
rest of the substance of the cytoblast.” — In connexion with these observations of 
f Dr. Henle has described the “ nucleus ” of pus and mucus globules as becoming cleft or divided by acetic 
acid into roundish or oval parts, each having a depression in the middle. (Valentin’s Repertorium, 1839, II. 
pp. 224, 225.) Compare with the minutest discs in Plate XXII. fig. 162. I think, however, that acetic acid 
shows rather the existing state of the object in question ; this being in pus the eccentric nucleolus of a cell. 
Besides, the present memoir is full of facts demonstrating that division is a natural mode of reproduction of the 
nucleus and nucleolus, and apparently common to these objects everywhere. (All the figures which accom- 
pany this paper represent objects as seen without the addition of any substance whatever. They were viewed 
lying either in fluid from the Graafian vesicle, or in mucus from the oviduct.) 
