374 
Notes . 
attached to the phenomenon until very recently. Within a year, two 
investigators have attempted to base somewhat important views upon 
the observation of nucleolar masses beyond the limits of the nucleus 
during karyokinesis. Zimmermann 1 attempts to demonstrate that the 
occurrence of nucleoli in the cytoplasm during nuclear division is 
a typical phenomenon, and, regarding the nucleoli as permanent and 
definite organs, he holds that they are thrown out during division and 
again taken up into the daughter-nuclei resulting from the division. 
Thus he comes to regard all nucleoli as derived from previous ones 
and, extending the generalization accepted for the cell and the 
nucleus, to write 1 Omnis nucleolus e nucleolo/ 
Karsten 2 appears to have observed a similar condition in spore- 
mother-cells of P silo turn , and to have been led by the manner of their 
occurrence to regard the nucleolar masses as identical with the 
centrospheres, first described for plant-cells by Guignard ; though he 
admits that they occur far less definitely and regularly than Guignard 
has described. 
It is well known that the bodies known as nucleoli may be readily 
distinguished from other constituents of the vegetable cell by means of 
suitable staining media, so definitely as to leave little room for uncer- 
tainty. They take a blood-red colour on exposure to a mixture of 
fuchsin and iodine-green, and subsequent treatment with alcohol 
containing iodine and acetic acid 3 intensifies the selective staining. 
For fixing material for cell-studies nothing is better, as a rule, than 
alcohol of 95 per cent, or higher. 
The studies of various tissues of several plants has led me to the 
conclusion that the extrusion of nucleolar substance during karyo- 
kinesis, far from being a normal occurrence, is a very exceptional one ; 
and that the persistence of recognizable masses of this substance 
during division is so unusual as either to have a pathological signi- 
ficance or to indicate incomplete or unsatisfactory fixation of the 
material. The nucleoli usually disappear before the breaking down of 
the nuclear membrane and reappear after the constitution of the 
daughter -nuclei. Their entire behaviour is such as to justify but one 
1 Ueber das Verhalten der Nucleolen wahrend der Kerntheilung : Beitr. z. 
Morph, u. Phys. d. Pflanzenzelle, Bd. II, Heft i (1893). 
2 Ueber Beziehungen der Nucleolen zu den Centrosomen, &c., Ber. d. D. bot. 
Ges., Bd. XI, p. 555 (1894). 
3 Zimmermann, loc. cit. 
