32 
Wager.— The Nucleolus and Nuclear Division 
Mann 1 considers it probable that the nucleus and nucleolus are con- 
cerned in the assimilation of food-material, and that the nuclear chromatin 
may be less highly elaborated material than the nucleolar chromatin. He 
suggests that the nucleolus may be either ‘ an organ for the further trans- 
formation of substances already elaborated by the nucleus, or simply 
a storehouse for food-material, which has been already transformed by the 
nucleus into substances directly available for the nourishment of the 
achromatic elements of the cell.’ 
In Spirogyra , according to Tangl 2 , Meunier 3 , Moll 4 , Decagny 5 , 
Henneguy 6 , Mitzkewitsch 7 , and Van Wisselingh 8 , the nucleolus contains 
chromatin and the chromosomes are derived entirely or in part from it. 
Moll points out that only the nucleoli retain gentian violet with 
obstinacy ; from all other parts it is extracted without difficulty. The 
nucleoli are found in three different forms — (i) homogeneous, (2) vesicular, 
(3) exhibiting a skein structure. The last is the more common. Chromatic 
substance does not exist to an appreciable amount outside the nucleolus. 
The nuclear segments are formed by the transference of the chromatic 
substance from the nucleolus into the nuclear plasm. ‘ It seems as if the 
chromatic substance were squeezed from the nucleolus by an aperture 5 
into the nuclear plasm in which it appears ‘ as small fragments, ranged 
in an intermediate, achromatic thread, like the beads of a necklace ; and 
thus a skein, containing chromatic substance, is formed.’ 
Mitzkewitsch states that in the process of division the nucleolus 
increases in size, its membrane disappears and it becomes irregular in 
shape. It then becomes differentiated into a number of deeply stained 
granular chromosomes, which form the nuclear plate, and a less deeply 
stained substance in contact with them. In the daughter-nuclei the 
chromosomes can be distinguished still surrounded by this less deeply 
stained substance, with which they eventually become incorporated to form 
the daughter-nucleoli. 
A somewhat different account is given by Van Wisselingh, who 
believes that two only of the chromosomes are derived from the nucleolus, 
the others being derived from the nuclear thread. In the reconstitution 
1 The Embryo-sac of Myosurus minimus , L. A Cell Study, Trans, and Proc. Bot. Soc. 
Edinburgh, 1892. See also Brit. Ass. Reports, 1892, p. 753. 
2 Ueber die Theilung der Kerne in Spirogyra-ZellQu. Sitz. d. k. Akad. d. Wiss. in Wien, lxxxv, 
1882, p. 268. 
3 Le nucl^ole des Spirogyra. La Cellule, 1888. 
4 Observations on Karyokinesis in Spirogyra. Verhand. der k. Akad. van Wetenschappen te 
Amsterdam, 1893. 
5 Bull. Soc. Bot. France, xlii, 1895, p. 319. 
6 Lemons sur la Cellule, 1896. 
7 Ueber die Kerntheilung bei Spirogyra. Flora, lxxxv, 1898, p. 81. 
8 Ueber den Nucleolus von Spirogyra : ein Beitrag zur Kenntniss der Karyokinese. Bot. Zeit., 
lv, 1898, p. 195, and Flora, lxxxvii, 1900. 
