290 CALKINS. [Vol. XI. 



central part, derived from the centrosome and which ultimately 

 forms the tip of the spermatozoon, and second, the Alitosoma, 

 derived from the equatorial spindle fibres ( Verbindungsfdsern) 

 which ultimately form the membrane about the axial filament 

 of the tail. The tip of the spermatozoon, therefore, is formed 

 from the Nebenkeim. Moore ('94) confuses the two terms and 

 calls archoplasm a body originating from the spindle fibres 

 after the disappearance of the spindle. Henking ('9i) uses the 

 term Nebciikern in the sense of Butschli, but restricts it to the 

 body formed by the peripheral spindle fibres, while the central 

 spindle forms what he calls the Mitosoma. The Mitosoma in 

 Pyrrhocoris apteriis forms the tip of the spermatozoon, and the 

 Nebenkern a caudal membrane. Hermann ('9i) also gives to 

 the Nebenkern the significance of archoplasm, while Balbiani 

 (93) considers archoplasm, Nebenkern, and yolk-nucleus homol- 

 ogous bodies. Other spermatologists give various meanings 

 to the terms archoplasm and Nebenkern, making it difficult to 

 determine whether a certain element in a spermatozoon (as the 

 tip, for example) comes from the centrosome and archoplasm 

 or from the Verbindungsfdsern of the karyokinetic spindle. 



The Nebenkern in Lwnbricus usually lies at the extremity 

 of the cell opposite the archoplasm, and in some cases it per- 

 sists even during the process of karyokinesis (Fig. 45). 



The presence of archoplasm and Nebenkern in the same 

 cell in Lunibricus throws some light on the distinction be- 

 tween these bodies. These differences can be tabulated as 

 follows: (i) the Nebenkern originates as the remnant of 

 the interzonal fibres, while the archoplasm is a constant ele- 

 ment of the cell ; (2) the archoplasm plays a certain definite 

 role, while the Nebenkern has no apparent function ; (3) the 

 archoplasm divides and behaves during karyokinesis in the 

 same manner as a so-called centrosome and finally forms the 

 middle-piece of the mature spermatozoon, while the Nebejikem 

 is passive and disappears after a seemingly useless existence. 

 These distinctions are not true, however, for all forms. In 

 many cases the Nebenkern has an important function, such as 

 the formation of enveloping membranes in the salamander 

 spermatozoa. 



