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 Braner (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 



