132 ON THE SPERMATOGENESIS OF THE SILK-WORM. 
nucleolus consists of four somewhat large chromatic bodies. 
These chromatic bodies arrange themselves in single or double 
rows, or sometimes very irregularly. Henking (15) also pointed 
out a case somewhat resembling this in a nucleolus of Pyrrho- 
coris apterus. 
When the primary germ-cells begin to divide, the fine 
net-work of chromosomes gradually becomes coarser (fig 19), and 
sometime after a beautiful skein stage is to be seen. I was 
not able to find, at this stage, the longitudinal splitting of the 
chromosomes, but this is clearly to be observed in such cells in 
which the nuclear segments can be distinctly made out (fig. 20). 
This corresponds to the segmented skein of Flemming. 
Although the chromosomes of the primary germ-cells have 
divided longitudinally in this stage, they do not separate 
from each other until they form the equatorial plate. The 
double chromosomes thus formed present the appearance of 
being only one when viewed from one side (fig. 21). When the 
division proceeds a little further, the chromosomes separate from 
each other and go to the poles (fig. 22). Owing to the small 
size of the primary germ-cells, the exact number of the 
chromosomes can not be made out. I was, however, enabled 
to count, in favorable specimens, twenty-six to twenty-eight 
chromosomes in polar views. 
The same mode of division, as now described, takes place 
many times in this stage, and the primary germ-cells become 
at last reduced to about two-thirds or less of their original size. 
II. The Growing Stage. In the first part of this stage, 
the genital elements are small, in consequence of the repeated 
karyokinetic divisions of the primary germ-cells. I call these 
cells by the name of sperm-mother-cells (“ Samenmutterzel- 
len”). In the resting stage (fig. 23), the sperm-mother-cells 
are similar in appearance to that of the primary germ-cells. 
A nucleolus is generally seen in the net-work of linin and 
chromatin. 
The sperm-mother-cells gradually enlarge, and their nuclei 
go through marked changes (figs. 24-46). 
Most of the chromatin granules become collected to one 
side of the nucleus, and form an irregular mass. Fine linin 
