DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
547 
observations with those of others, on the appearance and the destination of this very 
important structure, when it does not continue at the surface of the cell. 
378. The first question is, — which of the objects figured by rue in the present 
“Series,” correspond to the nucleus of authors? No one will doubt that the object 
eccentric in one of the twin cells Plate XXV. fig. 203, is to be considered as so cor- 
responding ; an object resembling the “ corpuscle” or nucleolus of Schleiden, being 
also present in its centre. Nor is it to be supposed that any question will arise as to 
the identity of that nucleus with the central nuclei in, for instance, the twin cells bs 
of Plate XXIV. fig. 191. It is obvious that they differed only in local situation; the 
nucleus in fig. 191. having passed to the centre of its cell. Thus far then my ob- 
servations accord with existing views ; but, I am compelled to say, not any farther. 
379. Schleiden remarks, that in its original position the nucleus (or “ cytoblast”) 
“accompanies the cell which it has formed through the whole vital process, if it be 
not (as in cells destined for higher development) dissolved and absorbed — cast off 
as a useless member. This disappearance of the nucleus takes place either in situ, or 
it is first thrown into the centre of the celi'f'.” 
380. Let us now trace the appearances presented by the nucleus, according to my 
own observations, after it has passed to the centre of the cell. In the ovum Plate 
XXIV. fig. 191, as seen highly magnified (fig. 192.), the outer portion of the nucleus 
seemed to consist of the foundations of new cells. The corresponding part in Plate 
XXV. fig. 199. had enlarged, and an inner part come into view. Fig. 200. presents 
an ovum in which the twin cells had become filled with concentric layers of objects, 
which on close examination were found to be no other than the foundations of new 
cells. From the presence of such objects in the nucleus Plate XXIV. fig. 187, and 
from the condition of the latter in fig. 193, and Plate XXV. figs. 194. 196, it will 
perhaps be admitted that, in these instances, the place of the original nucleus of the 
cell, or “ cytoblast,” was occupied by the foundations of other cells, which, in some 
cases, had been pushed further out by fresh sets arising in the interior. 
381 . Now in this “ Third Series ” of researches, I have not met with any nucleus in 
which the same succession of appearances was not either directly witnessed, or to be 
inferred. The germinal spot — obviously a nucleus — was particularly traced (pars. 
327. 328.), and the germinal vesicle found to fill with more or less incipient cells in a 
manner essentially the same as that just described. The substance surrounding the 
germinal vesicle, in the ovum Plate XXII. fig. 156, consisted of elliptical and flat- 
tened objects, having an interior not materially differing from that above referred to ; 
and a similar condition of that substance will be found in many other figures. 
382. But further, on closely examining the discs or foundations of cells successively 
coming into view in the manner above mentioned, we find in their interior a repeti- 
tion of the same appearances — the foundations of yet other cells. This I have at- 
tempted to illustrate in outline in Plate XXIII. fig. 177? which I beg to state repre- 
sents nothing theoretical, — nothing more than I have actually seen. For instance, 
f Appendix, par. 425. 
4 A 2 
