144 bulletin: museum of comparative zoology. 



converted into a rounded "Idiozom." Later the " Mitocliondrien- 

 korper" 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 difl^erential 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 Spitzensttick an, so dass nach 

 Heidenhainscher Farbung oft recht eigenartige Differenzierungen im 

 Spitzensttick entstehen. Gegen die Vollendung der Ausbildung des 

 Spermatozoons verteilt sich die farbbare Substanz vollkommen 

 gleichmiissig iiber das Spitzensttick; 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- 

 drienkorper," 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 Ues 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 Ues 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 spermatozoon. Such 

 structures have been described by Henking ('91, Pvrrhocoris), 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 chieflv from the mitochondrion, while 



