No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 387 
and less assimilative albuminoid material than the nucleolar 
chromatin. On the assumption just stated, we could explain 
also why we find ... at the time of maturation portions of 
nucleolar matter detaching themselves from the main nucleolus 
to undergo a peculiar gelatinous change. The gelatinous change 
would correspond to a conversion of the assimilative material 
into achromatic elements, an explanation which would also 
explain the disappearance of nucleoli during the division of a 
cell. ... I believe the hypothesis that the nuclear chromatin- 
segments and perhaps the nucleoli are organs for the conversion 
of assimilated material into material directly available for the 
achromatic elements of the cell to be not quite erroneous.” In 
the mechanism of cell conjugation: “The endonucleolar fibers 
running through the body-plasm of the two sexual cells . . . are 
brought into contact with one another whenever the pseudopo- 
dial processes of the two cells have met. As soon as an union 
of fibrils has taken place, each fibril will commence to contract 
similarly to a muscular fibril,” which results in drawing the two 
nuclei, afterwards also the two nucleoli, together; thus the 
endonucleolus is the “ tropic center ” of the cell. 
Rosen (’92a) studied the differential staining of the nuclear 
elements in plants. Flowers of Scilla: in the nuclei of the 
“ Biindelparenchym ” are numerous large nucleoli, which differ 
in form and size; the one or two larger ones, “ Eunucleoli,” are 
each surrounded by a clear space, but none is present around 
the smaller “ Pseudonucleolen.” With the double stain, Alt- 
mann’s acid fuchsine and methylen blue, the Eunucleoli stain 
red and the Pseudonucleoli blue, or vice versa. Similar cells 
of Hyacinthus: by the application of the double stain, aqueous 
solutions of fuchsine and methylen blue respectively, the 
Eunucleoli stain red, the Pseudonucleoli blue ; but when these 
stains are applied in the reverse order, the nucleoli stain 
reversely. He considers, following Auerbach (’90), that the 
Eunucleolus is erythrophilic, the Pseudonucleoli kyanophilic, 
the latter staining as does the chromatin network. “Meine 
Pseudonucleolen aber sind eben offenbar weiter nichts, als 
besonders selbstandig ausgebildete Bestandtheile des chroma- 
tischen Kerngeriistes und sind wie dieses und sein Produkt, der 
