On the nucleolus and karyokinesis in 
Zygnema. 
Ninth contribution to the kwowledge of karyokinesis. 
by 
C. VAN WISSELINGH. 
Wibhilst Spirogyra has very often been used for the 
investigation of the nucleus and nuclear division, Zygnema 
has so far as I know, up to the present, only been studied 
for this purpose by two investigators. It should be no 
cause for surprise that the latter alga has generally been 
neglected. The dimensions of the cells and nuclei are so 
much smaller than those in the larger species of Spirogyra, 
that one would expect to meet with still greater difficul- 
ties in a karyokinetic investigation than would arise in 
the case of Spirogyra. Such is indeed the case and in 
studying karyokinesis [I have not been able to trace the 
details of the process to the same extent as in different 
species of the genus Spirogyra. 
Mabel L. Merriman!) was the first to study karyoki- 
nesis in Zygnema. She could not with certainty identify the 
species studied, because she had no zygospores at her 
disposal. The chief results of her inquiry were as follows. 
She found in the nucleus of Zygnema no body that 
corresponds to the nucleoli of higher plants. There is in 
1) Mabel L. Merriman, Nuclear division in Zygnema. Reprinted 
from The Botanical Gazette, 41, Jan. 1906, p. 43—53. 
Recueil des trav. bot. Néerl. Vol. XI. 1913. l 
