No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 289 



the Nebenkent originates as the remnant of the interzonal 

 fibres of the karyokinetic spindle, and that it is, therefore, 

 archoplasmic in origin. In pancreas cells, Nussbaum ('82) 

 showed that the Nebenkern is derived by a budding off 

 from the nucleus and is therefore of nuclear origin. The so- 

 called Nebenkern in the &g^ cell originates in the same 

 manner apparently as in the pancreas cells. Valaoritis (-82) 

 described this body as originating by metamorphosis of the 

 germinal vesicle ; Van Bambeke ('93) claimed that it arises by 

 direct transportation of the chromosomes ; and in a recent 

 preliminary paper I ('95) have shown that this body (which 

 Carusin 1850 called the "yolk-nucleus" (Dotterkern) originates 

 from the chromatin network in the nucleus. Here also the so- 

 called Nebe7ikern of Blochmann is nuclear in orisfin. It is 

 apparent therefore that these bodies which differ so greatly in 

 their origin should not have the same name. In the ^g^ cell 

 the so-called Nebenkern is sufficiently well described by the 

 term ''Dotterkern' or "yolk-nucleus," and a more satisfactory 

 name can be found for the so-called Nebenkern of the pancreas. 



The word Nebenkern, if used at all, should be applied to the 

 element of the spermatic cell as originally proposed by Butschli 

 ('71), and I shall adhere to this use of the term in the present 

 paper. 



A Nebenkern, then, can be described as an element of the 

 early spermatic cell originating from the interzonal fibres 

 ( Verbindungsfdsern) of the karyokinetic figure. It must, there- 

 fore, be archoplasmic in origin, for the Verbindungsfdseni are 

 derived from the archoplasm. Its function, however, as archo- 

 plasm, is lost. 



That there is need of such an accurate definition of the term 

 Nebenkern in spermatic cells is well shown from the confusion 

 caused by its rather loose application in many instances. For 

 example, Platner ('85, '89) in his several papers on spermato- 

 genesis uses the term Nebenkern as the equivalent to Boveri's 

 ('84) Archoplasnia. This body as described by him, however, 

 seems to be equivalent to both archoplasm and Nebenkern, for 

 according to Platner's observations it consists of two parts, both 

 coming from the archoplasmic spindle. These are first, a 



