I32 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. Hcnking (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 ig), 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 



