SPERMATOGENESIS OF PASSALUS CORNUTUS. 413 



often shows a granular structure. It often shows a lighter 

 central portion which represents the position the spindle had 

 occupied (Fig. 2od). Soon after the Nebenkern has become a 

 spherical body, it begins to show a peripheral lighter area which 

 is of a vacuolar nature (Fig. 19). As the spermatid elongates 

 the Nebenkern becomes elongated and the vacuolization of the 

 peripheral layer becomes more marked (Fig. 20, a, &). It be- 

 comes divided into two halves and is later pierced by the axial 

 filament (Figs. 21, 39). As the axial filament grows out, the 

 Nebenkern continues to elongate forming a sheath about it. 

 The material of the Nebenkern thus extends from the centro- 

 some for a considerable distance along the axial filament (Fig. 

 22). Fig. 20, c is that of a cross-section through the tail of a 

 spermatid showing the two halves of the Nebenkern on each side 

 of the axial filament. Whether or not the Nebenkern sheath 

 extends to the free end of the axial filament could not be deter- 

 mined. As the transformation continues, the Nebenkern be- 

 comes more lightly staining, and all evidences of its mitochondrial 

 nature are lost. 



3. Discussion. I have been unable to obtain any definite 

 and conclusive evidence as to the manner in which the mito- 

 chondria arise. There can be no doubt that they increase in 

 numbers during the growth period, and the question arises: to 

 what influence do the mitochondria ow r e their origin? This has 

 been and still is a much-debated cytological question, and much 

 depends on the final solution of the problem. 



Meves, Bouin, Duesberg and others have always maintained 

 that the mitochondria are persistent and self-perpetuating 

 structures, much as the chromosomes of the nucleus are at 

 present regarded. On the other hand, Goldschmidt and his 

 pupils, Buchner, Jordan, Wildman and others have derived the 

 mitochondria from the nucleus, and have thus maintained that 

 they are akin to the chromidia of Hertwig. Vejdovsky has 

 traced their origin from the sphere material, while Montgomery 

 in Euschistus concludes that they are probably derived from 

 the idiozome or the nucleus, or by a "joint action" of both. In 

 their studies on the living sperm cells of Chorthippus, Lewis and 

 Robertson are unable to find any evidence that the mitochondria 



