blackman: the spermatogenesis of scolopendra. 113 



Butschli ('71 a , '71 b ), La Yalette St. George ('86, p. 9), Platner ('89), 

 Henking ('91), Wilcox ("95, '96), Erlanger ('96 1 '), Paulmier (,'99;. Baum- 

 gartner (:02) and others, the Xebenkern i*esults from the direct metamor- 

 phosis of the interzonal filaments. Tin: remnants of the spindle are not 

 dissolved and subsequently reassembled to constitute this body. More- 

 over in insects, the centrosome is at the pole of the cell opposite to the 

 Nebenkeru at the time of the origin of that body. 



In Scolopendra the archoplasmic mass is quite different in origin. It 

 first appears upon the side of the cell opposite that at which the mid- 

 body was last seen, and it always arises in very close relation with the 

 centrosome. In fact, it partakes more of the nature of an idiosome than 

 of a Xebenkern. Moreover, in Scolopendra it does not arise directly 

 from the spindle remnants, — i. e. from archoplasm iu the fibrous con- 

 dition, — but from archoplasm which has been dissolved and now reap- 

 pears in the granular condition characteristic of so-called resting cells, 

 and at a stage later than that at which the interzonal filaments disap- 

 peared. Therefore I speak of this mass not as Xebenkern or idio- 

 some, but as undifferentiated archoplasm. It cannot be the Nebenkern 

 because of its origin, and I do not consider it a true idiosome because of 

 its very irregular shape, variable size, and undifferentiated character. 



B. Faserkorb. 



While none of the workers upon myriapod spermatogenesis have de- 

 scribed a Xebenkern in the spermatids, Tonniges (Korschelt und Heider, 

 :02, p. 527) finds in Lithobius, at the stage when the nucleus is begin- 

 ning to elongate, a differentiation — apparently a condensation — of the 

 protoplasm, which is probably comparable with the so-called Faserkorb 

 (Schwanzmanschette) of mammals described by Meves and other authors. 

 He also calls attention to its similarity to the Xebenkern of Paulmier 

 ('99), notwithstanding the difference in origin. "Das Bild (Xebenkern) 

 zeigt jedenfalls mit den bei Lithobius auftretenden eine sehr grosse 

 Aehnlichkeit." The structure described by Tonniges is the same as that 

 shown in my Figures 96—109, winch in Scolopendra is derived from that 

 portion of the archoplasm which remains after the greater part of it has 

 either passed around the nucleus to form the acrosome, or migrated back 

 along the axial filament. I agree with Tonniges that this structure, 

 although in many stages similar to the Xebenkern of insects, is not 

 homologous with it. In Scolopendra, however, the fibres — or later, the 

 membrane formed by the union of the fibres — do not attach themselves 



