136 ON THE SPERMATOGENESIS OF THE SIKL-WORM. 
The sperm-mother-cells with large chromatin granules and 
distinct centrosomes, described in the last part of the grow¬ 
ing stage, now entirely lose their nuclear wall and the chro¬ 
mosomes become arranged in an equator of the spindle form¬ 
ing a “ Kernplatte ” of Strasburger. In this stage, I have 
not found any nucleolus in the “ Kernplatte,” while Hen- 
king observed it in a spermatocyte of Pyrrhocoris apterus. 
Fig. 50 shows a side view of this stage. The chromosomes are 
arranged in a single row in the equator of the spindle, and 
not in double rows as Henking (15, 16) and vom Rath (28) ob¬ 
served in genital cells of Gryllotalpa, Pyrrhocoris and Pygaera. 
In a polar view of “ Kernplatte,” we can clearly distinguish 
twenty-eight chromosomes (fig. 52) in most of the cells, although 
some with twenty-six or twenty-seven are sometimes to be found. 
Each of the chromosomes of the “ Kernplatte,” gradually pro¬ 
duces a constriction in the middle of the long axis and forms a 
dumb-bell-shaped chromosome (figs. 50', 51). This constriction 
deepens until two chromosomes are formed. This mode of divi¬ 
sion corresponds very well with the division of sperm-mother- 
cells of Diaptomus described by Ishikawa in the following words: 
“ In the process of division each dumb-bell-shaped chromosome 
elongates and becomes divided in its middle part, so that one 
half of the dumb-bell goes to one pole and the other half to the 
other. The only difference from the ordinary karyokinesis con¬ 
sists in the mode of division of the chromosomes, which general¬ 
ly divide longitudinally and not transversely.” In fig. 50' is a 
“Kernplatte” of a cell in which the process of the transverse 
division of the chromosomes is to be seen. This is certainly an 
intermediate stage which is described in fig. 50 and fig. 51. After 
the transverse division, each row of chromosomes gradually re¬ 
cedes to the pole and forms a diaster stage (fig 53). This corres¬ 
ponds to the first reducing division of Weismann, each daughter 
nucleus containing also twenty-eight chromosomes as the mother- 
cells. Consequently, in this division no reduction of the number 
of chromosomes takes place, as Henking observed in the egg-and 
sperm-cells of many other animals (15, 16), while it corresponds 
very well with the first division of a sperm-mother-cell of Ascaris 
and Gryllotalpa described by O. Hevtwig (18) and vom Rath (28). 
After the division the chromosomes form a somewhat granular 
