SPERMIOGENESIS OF HELIX ARBUSTORUM. 
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spheres, reach the poles of the cell, and become connected by a central 
spindle. The chromosomes still occupy their former position, or they 
change it but little (Pl. IX., Fig. 9.), but they soon arrange themselves 
in the equatorial plate of the spindle. I show the metaphase on three 
figures (Pl. IX., Figs. 6. to 8.), Fig. 6. showing a little earlier, Figs. 7. 
and 8. a somewhat later stage. The chromosomes bying in the equato¬ 
rial plate are at first irregular in shape like the former, but they become 
later more regular, ovoidal, and arrange themselves parallel with their 
longer axes to the axis of the spindle. 
The chromosomes divide parallel to their longer axes. The division 
is scarcely to be seen from the side, but it is very evident in sections 
which show the spindle from the poles. We find the chromosomes on 
such sections (Pl. X., Fig. 1.) tied. The incision corresponds to the 
plane of division. The last mentioned figure shows an abnormal cell 
with two spindles which are at right angles to each other. Such cells 
are not rarely to be found, and their origin may be led back to the 
imperfect division of the spermatogonia. 
The centrosome is well visible on each figure. We see stained on 
Pl. IX., Fig. 7., which was drawn from a more strongly washed pre¬ 
paration the centriole alone, surrounded by a clear area. This area is 
equivalent to the centrosphere (s. PL IX., Fig. 9.). The centrosphere is 
on the two other figures stained by the iron hematoxylin ; they are 
irregular in shape. 
We can distinguish in the metaphase three kinds of chromo¬ 
somes : 
1. The ordinary chromosomes; thei** number is, as seen above, 
with the greatest probability 24; 
2. two very small chromosomes (PL IX., Figs. G., 8.) which pass 
during division into different daughter cells. They take their origin 
from an unpaired chromosome which can be seen already at the end 
of the prophase, and which is characterized by its smaller size (PL 
VIII, Fig. 9., the smallest, spherical chromosome); 
3. an unpaired chromosome, or chromosome-like body which at 
the end of the metaphase becomes cast out into the cytoplasm (PL IX., 
Figs. 6., 8.). 
These two latter kinds of chromosomes will be discussed later. 
The chromosomes after dividing pass to the poles of the spindle 
(PL IX., Fig. 10.). Several chromosomes are longitudinally incised, thus 
they appear to be divided. It is most probable that this incision indi¬ 
cates the plane of the second maturation division. A similar appearance 
is to be observed in Enter oxenos, the chromosomes of which, according 
