ON THE SPERMATOGENESIS OF THE SILK-WORM. 
145 
können nicht von Pol zu Pol ziehen, sondern werden in der Nähe 
des Spindeläquators durch ihren Ansatz an die sich färbenden 
Kernbestandtheile eine Unterbrechnung erleiden müssen.” 
The “Nebenkern” is according to la Vallette derived from 
cytomicrosomes, where he says (35) “ hier wie dort ganz 
unzweifelhaft seine Entstehung aus dem körnigen Zellplasma zu 
constatieren,” while Platner (26) assigns its origin to the nu¬ 
cleus. On this point he says: “ Hier entwickelt sich aus dem 
Kern ein eigenthümliches, an frischen Preparaten glänzendes, 
durch dunkleres Aussehen und homogene Beschaffenheit von 
dem umgebenden Protoplasma sich unterscheidendes Element. 
Es ist der Nebenkern in seiner ersten Anlage.” Beside this 
he (27) describes in the cytoplasm of the spermatocytes of 
Lepidoptera, a structure which he designates by the name of 
“ Verbindungsbrücken.” 
In the sperm-mother-cells of the silk-worm, we also find a 
body which has the same appearance as both Platner s “ Verbin¬ 
dungsbrücken ” and his centrosome. As it is present in the 
cytoplasm even after the appearance of two centrosomes, it is 
not a centrosome, so I will call it the “ Verbindungsbrücken ” 
after Platner , although this body is sometimes found within the 
cell and not always between the two neighbouring cells. It is a 
round body surrounded by a free plasm and staining very deeply 
by methylen-blue or Böhmer’s hæmatoxylin. There is generally 
only one but sometimes two. Rarely it has a constriction form¬ 
ing a dumb-bell-shaped rod. When it is present in the cyto¬ 
plasm, it corresponds very well with the centrosome of Platner 
(25) who observed it in many Lepidoptera (cf. his figs. 3, 4, 
5). After the complete formation of the spindle, it dissolves 
and is no more to be seen. Up to the present the function of 
this body is quite obscure and requires further investigations. 
Besides the “Verbindungsbrücken” we observe in the 
cytoplasm an aggregated spot of microsomes which afterwards 
changes into the central spindle. It resembles very much in 
shape the “Nebenkern” of la Valette (35, 36) and originates also 
from the cytomicrosomes. Hermann (17), Solger (32), Platner 
(25) Ishikawa (22) and others consider the “Nebenkern” to be 
a centrosome with archoplasm. This seems to be the case in 
Panulirus japonicus referred to above. But the structure known 
1 
