The Morphology and Physiology of the Nucleolus. 119 
and multilobul&ted. It breaks up into a number of unequal parts, 
which do not as a rule contain nucleoli. Nuclear fragmentation 
is not followed by mitosis, as it appears to be a degenerative 
process. 
During mitosis, the nucleolus may be cast out into the cyto- 
plasm, where it persists for a time — Gjurasin {17), Karsten {31 ) — 
or it may divide and the pieces pass into each daughter nucleus, 
as described by Schaudinn {4 9 ) in Amoeba crystalligera , by Winge 
{6f) in the slime fungus Sorodiscus , and by Keuten {33) in Euglena. 
More often preparatory to the formation of the chromosomes, the 
nucleolus disintegrates and disappears. The persistence of an 
argentophile core in such cases, described by Carleton {5), has 
already been referred to, but persistence of the nucleolus as a 
whole, during mitosis, is atypical. The process of dissolution of 
the nucleolus preparatory to chromosome formation, raises the 
very difficult problem as to whether there is any functional rela- 
tionship existing between nucleolus and chromosomes. At all 
events, when such stains as methyl-blue eosin are used, the newly 
constituted chromosomes now stain with eosin. Montgomery {43) 
says of this peculiarity that it “may be explained either by the 
assumption that the whole or part of the nucleolar substance 
unites chemically with the chromatin, or that it simply penetrates 
into the meshes of the latter.” It does not, however, “ appear so 
to unite chemically, and therefore the chromatin does not carry it 
over into the daughter cells.” 
The whole matter is very difficult to understand, and there is 
considerable divergence of opinion on the part of those who have 
specially studied this problem. 
3. Nucleolar Extrusions in Somatic Cells . — The extrusion of 
portions of the nucleolus during oogenesis has been described by 
a great number of writers, and this aspect of nucleolar behaviour 
has been discussed by me in a previous paper (3 If). Examples of 
extrusions in somatic cells are more rare, but several cases have 
been described within recent years. Montgomery {43), who made 
an extensive survey of the literature on the nucleolus up to 1898, 
refers especially to the work of Lukjanow {36), who described 
nucleolar extrusions in the stomach mucosa of Salamandra, and 
Humphrey {38), who observed the same phenomenon in plant cells. 
Of interest, also, is his account of the observations of Steinhaus 
{54), who from a study of the intestinal cells of Salamandra con- 
cluded that there was a plasmosome extrusion in these cells, and 
that the extruded plasmosome substance increased in size by 
imbibition, and combined with karyosomes to form a new nucleus. 
Such a process recalls to mind the formation of secondary nuclei 
in insects to which reference has already been made. 
One of the most remarkable cases of nucleolar extrusion is 
that described by Montgomery {43), in the subcuticular gland 
