ON THE SPERMATOGENESIS OF THE SILK-WORM. I33 
fibres with scanty chromatin granules are seen radiating from 
the mass to the wall of the nucleus. This is shown in figs. 24-26. 
The nucleolus, lying either in the chromatin mass or out¬ 
side of it, persists, as is unusual in skein stages of other animals, 
till to the end of the skein stage shortly to be described. 
The chromatin granules once collected into a single irregu¬ 
lar mass, become again separate from each other and arrange 
themselves along the radiating linin fibres, and the skein stage 
is thus obtained (fig. 27). In the nucleus of this stage we can 
easily observe Rabl’s pole-field. 
The same change of nucleus of the beginning of the growing 
stage was observed by Brauer (4) in Ascaris megalocephala 
where the longitudinal splitting of chromosomes was also 
observed. I have carefully searched after this in Bombyx, but 
could not find it in any of the skein stages. 
The most singular thing about here is that the chromatin 
substances once more go through changes similar to those 
now described. In fig. 28 the chromosomes again have lost 
their even outline, and present a granular appearance. They 
became moreover much shorter than before. These granulations 
soon become more defined, and their lineal arrangement is 
gradually destroyed until the nucleus presents the appearance 
shown in figs. 28', 29. The nucleolus, however, shows no change 
from the first resting stage till the present stage, and always 
consists of small chromatic granules imbedded in a less stainable 
matrix (figs. 23-29). Hand in hand with these changes of the 
nuclear substances, the cell-body gradually enlarges, but no 
metamorphosis of the cytoplasm is as yet to be recognized. 
The chromatin granules scattered in the nucleus become 
again collected in the centre of it and present an irregular mass 
as before. The position of a nucleolus, or two nucleoli, is also 
either in the centre of the mass of the chromatin granules or 
outside of it in the cavity of the nucleus (fig. 30). 
The same structure of the sperm-mother-cells as now de¬ 
scribed is also found in Papilio xuthus, P. alcinous, Calygura 
japonica, and Rodia fugax. 
In a still later stage, the chromatin granules again com¬ 
mence to separate from one another, and the nucleus again pre¬ 
sents the appearance shown in figs. 31 and 32. In most cases 
