146 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¬ 
bindungsfäden ” 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 zurück.” 
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 Flemming (8), Hœcker 
(12), Henking (14, 75, 16), O. Hertwig (18), Ishikawa (20) Platner 
(15, 27), and vom Rath (28, 29), in many animals. Especially 
by the beautiful researches of O. 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 : 
“ i. Die Samenmutterzelle entspricht der Eimutterzelle 
oder dem unreifen Ei. 
“2. Während des länger dauernden Ruhezustandes des 
ansehnlichen bläschenförmigen Kerns der beiden Geschlechts- 
producte wird die Kernsubstanz gleich für zwei Zelltheilungen, 
die sich unmittelbar aufeinander folgen, in eigenartiger Weise 
vorbereitet. 
