in Dictyota dichotoma. 
169 
there is much to indicate that this amount is nearly the same 
in all nuclei, those of vegetative cells appearing on account 
of their smaller size richer in this substance. In the primary 
nucleus, during the prophase, there is never developed the 
rather regular and uniform chromatin-spirem, such as is 
present in the vegetative cells (compare Figs. 2 and 18), but 
instead the chromatin is collected into masses more or less 
isolated from which are eventually formed the chromosomes 
(Fig. 2). In the vegetative cells, on the other hand, there 
is developed a chromatin-spirem, as in the higher plants 
(Fig. 18). 
Karyokinesis in the Tetraspore Mother-Cells. 
The development of the karyokinetic spindle in the 
Phaeophyceae has been studied recently by Strasburger 
(’ 97 ), and by Farmer and Williams (’ 98 ) in Fucus , and by 
Swingle (’ 97 ) in Stypocaulon. 
In the vegetative cells of Stypocaulon , according to Swingle 
(1. c., p. 315), the first indication of karyokinesis is the division 
of a small deeply stained granule or granules, adhering closely 
to the nuclear membrane, from which kinoplasmic fibres 
radiate. This granule or pair of granules is probably homo¬ 
logous with the centrosome or microcentrum of Heidenhain, 
and possibly with the centriole of Boveri, and for the sake 
of convenience each body or pair of granules is spoken of as 
a centrosome. The division of the cluster of kinoplasmic 
radiations takes place simultaneously with the separation of 
the daughter centrosomes ( 1 . c., Figs. 9 and 2 , Taf. XV; Figs. 
13 and 14, Taf. XVI). This all happens before the cell- 
plate which follows the division of the nucleus is formed. 
After the formation of the cell-plate the daughter centrosomes 
have assumed their definite positions. The angular distance 
on the surface of the nucleus traversed by the separating 
daughter centrosomes varies from 180° to 135 0 in the different 
successive segments. While this is taking place, the chro¬ 
matin framework and the nucleolus undergo certain changes 
