I46 ON THE SPERMATOGENESIS OF THE SILK-WORM. 



as the " Nebenkern " appears not always to be a centrosome 

 surrounded by an archoplasm, as the " Nebenkern " of the silk- 

 worm above described, shows very plainly. The formation of 

 the "Nebenkern"' of the sperm-daughter-cell from the " Ver- 

 bindungsfiiden " of the sperm-mother-cell in the silk-worm con- 

 firms the opinion of Hermann who describes it in the sperma- 

 tocyte of Salamandra in the following words (17) : " unleugbar 

 dem Protoplasma entstammend, kehren die Fibrillen der Cen- 

 tralspindel bei Rekonstruction der Tochterkerne, radienartig 

 ausstrahlend, wieder in das Protoplasma zuriick." 



On the Reduction of Chromosomes. 



Since the theoretical consideration of Weismann (44), the 

 reduction of chromosomes in sperm-mother-cells has been con- 

 firmed by many eminent authors such as Plemming (8), Hcecker 

 (12), Henking (14, 75, 16), 0. Hertwig (18), Ishikawa (20) Plainer 

 (15, 27), and vom Rath (28, 29), in many animals. Especially 

 by the beautiful researches of 0. Hertwig's " Vergleich der Ei 

 und Samenbildung bei Nematoden " not only is this fact proved 

 but also the similarity of the development in both sperm- and 

 egg-cells has become clearly known. In general, our researches 

 on the spermatogenesis of Bombyx mori corresponds so exactly 

 with the descriptions given by these authors, that it seems almost 

 superfluous for me to publish them. I have deemed it, however, 

 worth while to record the results of my own investigations 

 because there are some points of controversy among the conclu- 

 sions arrived at by these authors. As the ground of this question 

 we will quote the researches of O. Hertwig on the Nematodes. 

 His summary is : 



" 1. Die Samenmutterzelle entspricht der Eimutterzelle 

 oder dem unreifen Ei. 



"2. Wahrend des langer dauernden Ruhezustandes des 

 ansehnlichen blaschenformigen Kerns der beiden Geschlechts- 

 producte wird die Kernsubstanz gleich fur zwei Zelltheilungen, 

 die sich unmittelbar aufeinander folgen, in eigenartiger Weise 

 vorbereitet. 



