No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 29 1 



The archoplasm as described above is apparently equivalent 

 to the central body (centrosome) and its archoplasm. There 

 is no indication that it is of the nature of a Nebejikern. Ac- 

 cording to Moore ('94) in the spermatogenesis of the rat, the 

 "archoplasm " originates from the spindle fibres of the preceding 

 karyokinesis, probably from the interzonal fibres, or, to quote 

 his own words : "Accordingly in the spermatogenesis of the 

 rat, the sphere seems to be divided into two parts, one made 

 up of nothing but the residual spindle fibres (archoplasm), and 

 another containing nothing but the centrosomes." Again : 

 " The centrosomes divaricate and assume their usual position 

 at the poles of the growing spindle, while the archoplasm 

 remains an inactive structure in the body of the cell." At 

 another place he says : " The archoplasm is reabsorbed into 

 the cytoplasm." In this account of the archoplasm he is 

 simply describing the Nebenkern as defined above ; its origin 

 from the spindle fibres, its lack of connection with the centro- 

 some, its final absorption into the cytoplasm and its inactivity 

 in the cell, — all these are phenomena of the Nebenkern and 

 not of an active cytoplasmic organ like the archoplasm of 

 Ltimbricus. It is not improbable that the same mistake is 

 made by others, and it may be found that the so-called " cen- 

 trosome" at the tip of the spermatozoon in many forms is in 

 reality a portion of the Nebenkern as Henking has described in 

 Pyrrhocoris apterus. 



Summary, 



The results of my investigation on the spermatogenesis of 

 Lumbriciis may be summarized as follows : 



1st. A multinucleate cell is formed in the testis. This 

 represents a group of the earliest spermatic cells or sperma- 

 togonia. Each spermatogonium gives rise to several sper- 

 matozoa. 



2d. The nuclei arrange themselves around the periphery of 

 the multinucleate cell. Cytoplasmic cleavages then ensue 

 between the nuclei, as in a centrolecithal ^g^. These cleav- 

 ages deepen until the nuclei are separated from the central 

 mass of the cytoplasm by mere filaments. 



