144 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
converted into a rounded “‘Idiozom.” Later the “ Mitochondrien- 
kérper” elongates to form a sheath around the axial filament, while 
the idiozome becomes applied to the anterior end of the nucleus and 
forms an anchor-shaped acrosome. In this brief paper Otte does not 
describe the formation of the acrosome in detail and, as he gives no 
figures, it is impossible to determine whether the process is similar 
in the two cases, but his reference to the differential staining of the 
acrosome would suggest that the process is much the same as in 
Steiroxys. ‘Die farbbare Substanz ordnet sich auf den verschiedenen 
Stadien der Ausbildung verschieden im Spitzenstiick an, so dass nach 
Heidenhainscher Farbung oft recht eigenartige Differenzierungen im 
Spitzenstiick entstehen. Gegen die Vollendung der Ausbildung des 
Spermatozoons verteilt sich die firbbare Substanz vollkommen 
gleichmissig tiber das Spitzenstiick; nur die vorderste Spitze er- 
scheint frei davon’’ (Otte, :06*, p. 753). 
Apparently the conspicuous spherical body in the spermatids of 
Steiroxys, which I have called Nebenkern, is comparable to the 
idiozome of Otte. This being the case, the small, irregularly shaped 
body which is applied to the nuclear membrane near the Nebenkern 
in the young spermatids would seem to correspond to the ‘ Mitochon- 
drienkérper,” although there is nothing in its appearance to suggest 
such a comparison. Following out this line of comparison still further, 
it would appear that the Nebenkern in the Acrididae is not comparable 
with the structure to which I have applied that term in Steiroxys, 
but rather to the small inconspicuous body which lies by the side of 
the nucleus, although in appearance the two are very unlike. If this. 
comparison is well founded, then there is nothing in the spermatids 
of the Acrididae corresponding to the body which I have called the 
Nebenkern in Steiroxys, and yet, with the exception of the nucleus, 
it is the most conspicuous element in the spermatid. On the other 
hand, the small indistinct body which lies beside the nucleus in Stei- 
roxys has the position and to a less extent the appearance of the body 
which has been described as the acrosome in the spermatids of various 
insects and traced into the anterior end of the spermatozoén. Such 
structures have been described by Henking (91, Pyrrhocoris), Paul- 
mier (’99, Anasa), Baumgartner (:02, Gryllus), Stevens (:05*, Steno- 
pelmatus). 
Regarding the origin of the Nebenkern in insects, there appear to be 
in general two views. La Vallette St. George (’86), Henking (91), 
Paulmier (99), Meves (:00, :02), Holmgren (:02) and Zweiger (:06) 
have found that it is derived chiefly from the mitochondrion, while 
