170 Mottier.—Nuclear and Cell Division 
which need not be mentioned here. During these processes 
also the dark bodies at the poles, which were previously 
dumb-bell shaped, have become thin and sharply bent at 
the middle ( 1 . c., Fig. 7, upper pole, and Fig. 10, Taf. XV). 
They are concealed by the densly crowded kinoplasmic fibres 
which penetrate the membrane and enter the cavity of the 
nucleus. 
These filaments, spreading out laterally, grow towards the 
centre of the nuclear cavity ( 1 . c., Fig. 17, Taf. XVI). At 
about this stage the very small, deeply staining chromosomes 
begin to collect at the ends of the entering fibres (1. c., 
Fig. 18, Taf. XVI). Even before the chromosomes collect at 
the ends of the spindle-fibres, it may be seen that they end 
in a blunt point, or in a little granule or knob whose diameter 
is, however, only slightly larger than the fibre. As the 
spindle-fibres penetrate further inward, the chromosomes 
are heaped up in an irregular mass near the centre of the 
nuclear cavity ( 1 . c., Fig. 20, Taf. XVI). The polar radiations 
are less pronounced and the nucleolus has entirely disap¬ 
peared. The next stage is that of the equatorial plate, where 
the chromosomes are arranged in a plane, others forming 
the base of two pyramids of spindle-fibres ( 1 . c., Fig. 21, 
Taf. XVI). 
Strasburger’s account of the formation of the spindle in 
Fucus is much less complete as to details, but there is no 
doubt that it is similar to that of Stypocaulon. 
In describing the process in Dictyota I shall begin with 
the first nuclear division in the tetraspore mother-cell at the 
time when the two centrospheres are on exactly opposite 
sides of the nucleus. 
As soon as the tetraspore mother-cell has increased suf¬ 
ficiently in size to be hemispherical in shape or even a little 
larger, and to appear very conspicuous beside the neighbouring 
superficial cells, as I have described in my preliminary note 
(Mottier, ’ 98 ), there appear on opposite sides of the nucleus 
two large, sharply-defined clusters or asters of kinoplasmic 
fibres radiating from a rod-shaped body often slightly bent, 
