No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 385 
a single large nucleolus, and during this process the nuclear 
sap gradually loses its staining power. He shows that when 
the nucleolar substance is dissolved in the nuclear sap, and 
after the cell division, a portion of this substance plays a part 
in the production of the cellulose walls of the daughter-cells ; 
but he holds that not all of it is thus consumed, but that the 
nucleoli have probably some other, as yet unknown, function. 
Mann (’91) introduces a new method of differential nuclear 
staining: when plant tissues are stained for ten minutes in 
saturated solution of heliocin in 50 jo alcohol, and then from ten 
to fifteen minutes in a saturated aqueous solution of aniline blue, 
the nucleolus is red, the rest of the nucleus and the cell blue. 
Macfarlane (’92) constructs the following hypothesis, based 
on previous observations of his own and of Mann: “We would 
consider, then, that the nucleolus is the special chromatic and 
cell center ; that it sends out fine radiating processes — the 
intranuclear network — which partially fuse externally to con¬ 
stitute the nuclear membrane, the interspaces of the network 
being occupied by nucleoplasm concerned in metabolic change; 
that radiating continuations of the chromatic substance pass 
out beyond the nuclear membrane and form a network in the 
protoplasm, while we would suggest for future proof or disproof 
that they further may be continued through wall pores to form 
an intercellular chromatic connection. . . . We would thus 
view a plant as a group of connected hermaphrodite cells, . . . 
bound together by a fine chromatic ramification, in the center 
of which in each cell is the nucleolus.” 
Mann (’92) studied the cells of the embryo sac of Myosurus 
minimus. At the commencement of the conjugation of the two 
nuclei resulting in the formation of the primary endosperm 
nucleus, each nucleus contains “ a large deeply stained nucleolus 
enclosed by a very faintly stained nucleolar membrane,” and 
in each nucleus are also one or two smaller globules, which 
“ seem to originate thus : when the nuclei about to conjugate 
have come in contact, one or two small nucleoli arise by the 
unequal division of the primary nucleolus. . . . These secondary 
nucleoli seem to have at first the power of division, but 
gradually they lose this power and their property of becoming 
