3i 
in the Root- Apex of Phaseolus . 
to a lower temperature, and Strasburger remarks that Hottes 1 has shown 
that a low temperature promotes the appearance of extranuclear nucleoli 
whilst a higher temperature promotes the formation of the spindle-figure. 
Zacharias 2 , in a series of important papers in which the structure and 
micro-chemical reactions of the nucleolus are dealt with, contends that by 
the action of digestive fluid nucleoli are clearly differentiated chemically 
from chromosomes, and that this difference is also brought out by staining 
in methyl green in which the chromosomes stain more deeply than the 
nucleoli. Nucleoli may be vesicular and may exhibit a differentiation of 
structure into a homogeneous peripheral portion and a more refringent, 
granular or vesicular central portion. They appear to consist of plastin 
with albuminoids, but contain no chromatin. By observations on the 
living cell, especially the rhizoids of Chara , he finds that the nucleoli 
disappear just as the nucleus is about to divide, and that, just before this 
happens, they undergo amoeboid changes of form. Several nucleoli appear 
in the daughter-nuclei, and these afterwards fuse together into one. No 
definite conclusions as to what becomes of the nucleolus during division, or 
its function can be stated. In the nucleolus of Spirogyra , which many 
observers maintain is morphologically connected with the formation of the 
chromosomes, he finds no chromatin ; but he remarks in his most recent 
paper that could such a morphological connexion between nucleolus and 
chromosomes be established it would follow from the combination of 
morphological and chemical data that during the formation of the elements 
of the nuclear plate definite chemical changes would take place. 
Carnoy’s observations 3 led him to distinguish four kinds of nucleoli — (i) 
‘nucleoles nucleiniens,’ (2) ‘ nucleoles-noyaux,’ (3) ‘nucleoles plasmatiques/ 
and (4) ‘ nucleoles mixtes,’ a combination of (1) and (3). He thinks that the 
plasmatic nucleoli may be concerned in the formation of the spindle. The 
‘ nucleoles nucleiniens } are part of the chromatin-network and may consist 
of an amorphous mass of chromatin or of a chromatin-thread. 
Macfarlane, in his earlier contributions 4 and in his latest 5 paper, con- 
tends that the nucleolus is the most specialized portion of the cell and 
contains the main mass of the chromatin-substance. 
1 Reduktionstheilung, Spindelbildung, Centrosomen und Cilienbildner im Pflanzenreich, p. 127. 
2 Zacharias, E., Ueber den Zellkern, Bot. Zeit., xl, 1882. Ueber den Nucleolus, Bot. Zeit., xliii, 
1885. Ueber das Verhalten des Zellkerns in wachsenden Zellen, Flora, lxxxi, 1895. Ueber einige 
mikrochemische Untersuchungsmethoden, Ber. d. deut. Bot. Gesell., xiv, 1896. Ueber Nachweis 
und Vorkommen von Nuclein, Ber. d. deut. Bot. Gesell., xvi, 1898. Ueber die achromatischen 
Bestandtheile des Zellkerns, Ber. d. deut. Bot. Gesell., xx, 1902. 
3 La biologie cellulaire. Etude comparee de la cellule dans les deux regnes. Lierre, 1884. 
La cytodi^rese chez les Arthropodes. La Cellule, i, 1885. 
4 Trans. Bot. Soc. Edinburgh, xiv, 1881. Trans. Royal Soc., Edinburgh, xxx, 1885, and xxxvii, 
1892. 
5 Current Problems in Plant Cytology. Contributions from the Botanical Laboratory, University 
of Pennsylvania, ii, 1901. 
