1904] MERRIMAN: VEGETATIVE CELL DIVISION 187 
positive evidence of bodies in the cytoplasm which can be inter- 
preted as centrosomes. 
THE NUCLEOLI. 
The nucleoli, generally two in number, can be seen in fixed 
preparations of quiescent cells lying within a clear space sur- 
rounded by the chromatic network. 
The size and shape of the nucleoli vary with the size and 
nature of the cell. Elongated cells have elongated nuclei and 
nucleoli (fig. 55), while the large central cells of the plerome 
have large, more or less spherical nuclei. 
This power of accommodation of the nucleolus to the shape 
of the nucleus, together with its vacuolization and amoeboid 
contour, are direct indications of its essentially fluid nature. 
Referring to fig. 50, the large nucleoli in a central cell of the 
plerome can be seen. As these central cells recede in their mul- 
tiplication from the zone of greatest growth, the nucleoli become 
relatively larger, the chromatic substance less conspicuous and 
abundant. 
From these observations two conclusions might be drawn. 
The nucleoli, enlarging either by intussusception or apposition of 
particles coming from the cytoplasm, by their own growth may 
rob the chromatin elements of the nutriment necessary to enable 
them to develop the chromatic figure. Hence degeneration 
results, the line of broken-down cells giving rise to the central 
cylinder. Or the nucleoli may be thought of as accumulations 
of a substance which results from the reduction and degeneration 
of the chromatin. The latter seems more probable, as all the 
evidence obtained from cells which retain to the last their capa- 
city for division points in the direction of a nucleolus arising from 
the disintegration of chromosomes into individual chromatin 
granules. 
Rosen (8) states that in the hyacinth the nucleolus melts 
away during the formation of the spindle. In one series of sec- 
tions only obtained from the hyacinth he found nucleoli cast into 
the cytoplasm. He offers the two following explanations for 
the difference in these series: special conditions of growth and 
nourishment might bring about the expulsion of the nucleoli 
