DR. MARTIN BARRY’S RESEARCHES IN EMBRYOLOGY. 
551 
face of the cell-wall does not commence, so far as I could observe, until after the ab- 
sorption of the cytoblast.” Now I would suggest that the “ cytoblast,” instead of being- 
absorbed, resolves itself into discs or cells, thus furnishing in the first place the con- 
tents of the cell (“ zeilen-inhalt”), and, through these, the deposits in question. The 
same observer states “the interesting result, that the [spiral] fibres never form free, 
but always in the interior of cells and I would offer the same suggestion with re- 
spect to these. 
391 . Schwann -f~ describes young cells in certain situations as at first perfectly trans- 
parent. “ Gradually, however,” says he, “they acquire a granular, yellowish appear- 
ance; and it is remarkable that this yellowish precipitate generally or always forms 
first around the nucleus.” Does not such “ precipitate” consist of the substance into 
which the free portion of the nucleus becomes resolved ? The same observer states]: 
that “ In the gill- cartilage of the Tadpole many cells present a minute nucleus 
having lacerated contours, which is perhaps the cytoblast of these cells undergoing- 
absorption.” I venture to believe, that it may be the nucleus resolving itself into 
cells. 
392. Schwann § observed nuclei in some instances to enlarge, as Schleiden had 
done in plants. Compare in the present memoir the size and condition of the nuclei 
in the twin cells ( bs ) of Plate XXIV. fig. 191. with those in Plate XXV. figs. 199. 
201 . 
393. Schwann has shown that in cartilage, cells occur in groups ||. With regard 
to these groups I would remark, that their appearance very much resembles that 
which would be presented by several generations of the twin cells of the germ (de- 
scribed in this memoir) inclosed the one within the other. And the resemblance 
suggests to me the idea that both result from the same process. Schwann offers as 
possible the following explanation. “These groups perhaps arise from two to four 
cells having formed in a parent cell, in which case each half of the cell-wall must 
consist of two layers, one of which corresponds to the wall of the parent cell, the 
other to the wall of the secondary cell ; so that thus each partition wall of two groups 
must consist of four layers” (/. c., p. 22.). Subsequently, however (pp. 113. 114.), 
he expresses doubt as to the sufficiency of such an explanation. We saw, in tracing 
the cells which successively enter into the formation of the germ, that very many of 
those into which the nucleus becomes resolved, disappear by liquefaction. Is it not 
possible — supposing cartilage to be formed by a like process — that, instead of lique- 
fying, the supernumerary cells contribute to the thickening of the walls of the parent 
cell? We have seen too (pars. 351 and 357-) that minute cells (apparently from the 
interior of liquefied parent cells) become introduced between enlarging cells (Plate 
XXIII. fig. 179, Plate XXIV. figs. 188. 189.) ; and also that, however minute, cells 
seem to give origin in their interior to other cells. Now if, instead of disappearing 
by liquefaction, the minute cells so introducing themselves between larger ones were 
f L. c., p. 24. - + L. c., p. 26. § L. c., pp. 27, 28. || L. c., tab. i. figs. 8, 9. 
