MUNSON: SPERMATOGENESIS OF PAPILIO. 
113 
In what has become regarded as a typical spermatozoon, the fol¬ 
lowing parts are usually thought to be present: (1) acrosome, l^ead, 
middle piece, tail; in the tail there is thought to be (2) axial filament, 
inner tail envelope, outer tail envelope. From what parts of the 
spermatid do these various parts arise? Wilcox (’96) found that 
in Caloptenus the middle piece arises from the centrosome. Paul- 
mier (’99) says: “A strict application of the term nebenkern (defined 
as a body formed from the spindle fibers and yolk granules) would 
include the acrosome, shortly to be described; for that also in insects 
appears to have a common origin with the part forming the tail sheath.” 
Of the centrosome, Paulmier says: “It thus seems quite certain that 
in Anasa it does not move around the nucleus, as Wilcox (’96) describes 
in Caloptenus, and as I have myself observed in Papilio. Later how¬ 
ever, a centrosome appears in the nebenkern, lying on the nuclear 
membrane.” 
It seems unfortunate that Paulmier has yielded to the temptation 
of drawing some of his most important conclusions, not from Anasa, 
the subject which he studied primarily, but from Papilio, a form 
which he appears to have examined only incidentally. My observa¬ 
tions on Papilio rutulus do not confirm these conclusions. 
There is a very extensive recent literature on the question of tetrad 
formation, reduction, and maturation. Henking (’92), Henneguy 
(’98), Wilcox (’95), and Paulmier (’99) have discussed this literature 
in their interesting studies. It is so well known by students of cytol¬ 
ogy, that I feel justified in omitting any discussion of it. Observa¬ 
tions on reduction are stimulated by the theory of Weismann. To 
argue extensively about the longitudinal and transverse splitting of 
the spherical chromosomes of insects such as I find in Papilio only 
suggests that facts are in danger of being suited to the theory rather 
than the theory to the facts. 
Mention must be made here of the so called Verson’s cell of the 
silk worm which the above authors do not mention, and which is 
evidently so closely related to the grandmother stem cell of the present 
work. 
Erico Verson (’89) first described in Bovibyx mori an enormous 
cell, located in the peripheral end of each follicle. According to 
him, it has an eccentric nucleus and the cytoplasm spreads out ra¬ 
dially. The cell divides amitotically and gives rise to all the formed 
elements of the testis. He regards it, consequently, as the true sperma¬ 
togone. 
