112 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Another important question which has attracted considerable 
attention, and given rise to much confusing discussion is the relation 
of the centrosome to this nebenkern and the part which either of these 
plays in the formation of the spermatozoon. Says Wilson (’02): “The 
nebenkern sometimes takes a definite part in the formation of the tail 
envelopes and of the acrosome (insects) but in many cases it seems 
to be wholly wanting.” In Papilio it takes no such part, and the 
fact that in many cases it is wholly wanting is easily understood when 
its ultimate fate in Papilio is considered. He says further: “The 
idiozome is in some eases an undoubted attractionsphere derived 
from the aster of the last division, and at first containing the centro¬ 
some as shown bv Calkins, (’95) and Erlanger, (’96, 4) in the sala¬ 
mander and guinea pig, Aleves (’96, ’99), and in Helix according to 
Korff (’99), though in later stages the centrosomes usually pass out 
of the body of the idiozome. In some cases the idiozomes of adjoining 
cells remain for a time connected by bridges of material representing 
the remains of the spindle, and hence corresponding to a nebenkern 
(e. g., salamander, Aleves, ’96), and the distinction between neben¬ 
kern and idiozone here fades away.” 
From my observations already recorded it is self evident that some 
of Wilson’s (’02) statements are misleading when he maintains that 
in insects the nebenkern takes a definite part in the formation of the 
tail envelopes and acrosome. Neither can the broad statements of 
La Valette St. George (’85) and Biitschli (’71) be strictly true when 
they maintain that in insects, the nekenkern forms the middle piece. 
• As I have shown that the nebenkern finally dissolves in the cytoplasm, * 
as Prenant (’88) also found in pulmonates, the general statement that 
the nebenkern forms the headpiece as maintained by Iveferstein (’66), 
La Valette St. George (’67), Aletschnikoff (’68), Duval in molluscs, 
Grobben (’78) in decapods, and by Nussbaum (’84) is not confirmed 
by the facts in Papilio. 
I have shown that it originates primarily from the intermediate 
spindle fibers of the last maturation division and that its persistence 
seems to be due to the elimination of chromatin granules during the 
last maturation division, which if it were not for the maturation divi¬ 
sions themselves would strongly suggest that it has something to do 
with reduction. This has also been suggested by van Beneden and 
Julin (’84) in Ascaris.. Both Waldeyer (’87) and Weismann (’64) 
have favored such an interpretation. 
