532 
MONTGOMERY, 
[Vol. XV. 
though the mode of disappearance of this substance may be 
more or less dependent upon the mode of mitosis, the substance 
of the parent-nucleolus may be in many cases not transferred 
to the daughter-nuclei, but the latter (perhaps as a rule) may 
produce their own nucleoli de novo. 
Strasburger (’93, ’97) assumes that the small granules found 
by Kostanecki (’92) in the equatorial plate of the central spindle 
may be nucleolar particles, and accordingly that the nucleolar 
substance may be in this way very evenly distributed to the 
daughter-nuclei; but it is not as yet clearly shown that these 
granules are derivatives of the nucleolus (cf also Debski, ’97, 
Sala, ’95, Pfitzner, ’86b, and Rosen, ’95). 
Zacharias (’85), Carnoy (’85), and Platner (’86) have concluded 
that in some cases the achromatic spindle fibers are derived 
from the nucleolus ; similar views are held by Strasburger (’95, 
’97), Harper (’97), and Fairchild (’97), but most facts would show 
this view untenable. 
Rhumbler (’93) assumes that a greater amount of nucleolar 
substance is accumulated in the nucleus before mitosis than is 
necessary for its growth, and this superfluous amount would 
serve for the formation of the nucleoli in the daughter-nuclei. 
12 . The Function of the Nucleolus. 
The attempt to deduce the physiological economy of a struc¬ 
ture from a mere study of its morphological relations is always 
difficult, and this is especially the case with regard to the 
nucleoli. 
Balbiani (’64) found contractile and discharging vacuoles in 
the germinal spot of Phalangium, and notes that they differ 
from the contractile vacuoles of the Rhizopoda in that they 
are not formed again at the same point. Hacker (’93c) regarded 
the nucleolus of the ovum of Echinus as an excretory organ, 
since he found its large vacuole to be contractile; he compared 
it directly to the contractile vacuole of Infusoria. Balbiani 
(’65b) also observed contractile vacuoles in the germinal spots 
of Helix , Vortex , and Prostomum , and in these the vacuole dis¬ 
charges through a small orifice in the cortical substance of the 
