in Dictyota dichotoma . 175 
centrosomes undergo a similar diminution in size. The 
invariable tendency of the chromosomes to collect and fuse 
into larger masses has made it impossible to determine 
accurately their number in this division. In the equatorial 
plate often only two large chromatin masses are seen (Figs. 14 
and 15), but from the number that can be clearly made out 
in the first division one cannot assume that these two masses 
represent only two chromosomes. 
The condition of the daughter nuclei presents nothing 
different from what has already been described for the pre¬ 
ceding mitosis. The connecting fibres likewise disappear 
entirely. 
Karyokinesis in Vegetative Cells. 
In vegetative cells it is far more difficult and time-consuming 
to obtain as complete a series of stages in the development 
of the spindle as I was able to observe in the tetraspore 
mother-cells, but a sufficient number was found to indicate 
without much doubt what the process is, and to furnish data 
for a comparison with what has just been described. 
The resting nucleus presents nothing out of the ordinary. 
Neither in the apical cell nor in any other was I able to 
demonstrate an aster or centrosphere at all times during 
the so-called resting period, but as soon as karyokinetic 
activity begins, an aster is always to be observed near the 
nucleus, even while the latter still presents the structure 
characteristic of the complete resting stage (Fig. 17). I have, 
however, observed the centrosomes with few but distinct 
radiations in the stalk-cell of a tetrasporangium, and often 
in other cells, which had been in the resting stage for a 
relatively long time, and which would probably not undergo 
further division. 
From the very fine and characteristic linin-reticulum there 
is developed a distinct chromatin-spirem as in higher plants, 
a condition which does not obtain in tetraspore mother-cells 
(Fig. 18). The spindle reaches maturity before the membrane 
of the mother-nucleus disappears (Fig. 19). At this stage 
