( 417) 
eylindrical wall was formed at a certain distance round onc of the 
nuclei, which consequently could for a small part only have been 
formed in the spindle. Finally we have the formation of the first 
pavement of endosperm-cells from the parietal layer of protoplasm of 
the embryo-sac as well in Fivtillaria as in many other plants. When 
the number of nuclei of this laver of protoplasm has very greatly 
increased, separations between the nuclei arise, so that a layer of flat, 
pentagonal or hexagonal cells is formed, which at last are separated 
from each other by cell-walls. These cell-walls are formed at a period 
when of the originally present nuclear spindles no trace is left. 
In relation with these facts the result of Mr. Sypkens about the 
negative part played by the nuclear spindle in cell-division cannot 
surprise us and it even gains in inner probability by them. This 
result also shows the way to a more profound study of the pheno- 
mena of cell-division and wall-formation in the vegetable kingdom. 
The cell-divisions in growing-points, in the above-mentioned epider- 
mal cells of ferns, also in the parietal layer of protoplasm of the 
embryo-sac, must now be more closely investigated, preferably by 
the method applied by Mr. Sypkens, and important results may be 
expected of this investigation. Also the study of living, dividing cells, 
in the same sense as was formerly done by Tree *) deserves again 
our attention in this respect. 
It is by no means impossible that by such investigations the con- 
ception of cell-division in plants will come still nearer to that of 
the same phenomenon in animals than is the case at present. 
From all that precedes it appears that the nuclear spindle is formed 
entirely from the ¢ytoplasm and returns to it. Besides, all investi- 
gators agree that in nuclear division the nuclear membrane and the 
nucleoli are dissolved and later are formed anew in the daughter- 
nuclei. An uninterrupted individual position with regard to the cyto- 
plasm is consequently, among all the parts of the nucleus, occupied 
by the chromosomes alone, only here there is question of a hereditary 
organisation. 
The opinion of some authors that the nucleus during the whole 
process of division would form an isolated whole with respect to 
the cytoplasm and that at first there would be a sort of vesicle, 
joining the daughter-cells and separating the spindle from the cyto- 
plasm, must consequently be abandoned. 
In relation with this IT may briefly point out the complete agree- 
1) M. Treus, Quelques recherches sur le rôle du noyau dans la division des cellules 
végétales. Publié par Académie Roy. Néerl. des Sciences. 1878. 
29 
Proceedings Royal Acad. Amsterdam, Vol. VIL. 
