in Lilium Mar tag on: II. Spermatogenesis . 205 
The number of the chromosomes taking part in the first 
karyokinesis of the pollen-mother-cell nucleus is most easily 
counted while they form a nuclear plate. A single longitudinal 
section from an anther of the right age contains hundreds of 
such figures, but there is some difficulty in exact counting, 
because the chromosomes are crowded on the spindle. 
I finally adopted the following method:— Two hand-sections 
were closely examined for spindles more or less perpendicular 
to the plane of the section. Before any attempt was made 
to count the chromosomes, certain tests were applied to each 
figure. The objective was raised until the whole nuclear plate 
was indistinct. If no part of the section in its neighbourhood 
was then in sharp focus, the figure was rejected. The same 
test was applied with a lowered objective. The object of both 
was to exclude nuclear plates lying on either surface of the 
section, for chromosomes lying above or below the others 
might have been removed from such figures in cutting the 
section. Nuclear plates which stood these tests, but in which 
the chromosomes were crowded together on one side, were 
also rejected. Twenty nuclear plates were chosen in this way. 
In 9 cases there were certainly 1 2 chromosomes. 
„ 9 cases „ either 11 or 12 „ 
„ 1 case „ „ 12 or 13 „ 
„ 1 case ,, „ 10, 11 or 12 „ 
The daughter-nuclei formed by the first division never enter 
the resting-stage. Each is merely a close knot of chromatic 
ribbon, without nucleoli but enclosed in a nuclear membrane 
which disappears in the earlier stages of karyokinesis. 
When a daughter-nucleus is about to divide, it begins to 
swell up, and its chromatic coils become looser. As they 
separate, a certain symmetry is seen in their arrangement 
(Fig. 16). The coils now become stretched in the direction 
of the axis of the future spindle (Fig. 17) ; but the distortion 
is very slight compared to that of the corresponding stage in 
the micropylar daughter-nucleus of the embryo-sac. There 
the young chromosomes have a knotted and strained appear- 
ance, which is absent from those we are considering (cf. Fig. 
