No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 279 



The further history of this stage is as follows : during the 

 ensuing cell division (Figs. 22-27) the " Vierergnippeii" are 

 halved, sixteen double chromosomes going to each daughter 

 cell. Whether this is a reducing division in the Weismann 

 sense cannot be ascertained. It is interesting to note that in 

 no case is the axis of the spindle directed towards the center 

 of the spermatosphere (Figs. 5 and 43). The division planes 

 are radial and the daughter cells thus remain attached to the 

 blastophore. 



The reduction in the number of chromosomes has now taken 

 place, not during mitosis, however, but during the antecedent 

 period and through the activity of the chromosomes them- 

 selves. The process thus corroborates the view advocated by 

 Boveri (-89) and sustained by Brauer ('93) and others, that the 

 chromatin particles have power to arrange themselves. The 

 formation of the " Vierergricppen,'' however, differs from that 

 which takes place in Ascaris. 



Two main conceptions of the " Vierergnippen" and their 

 mode of origin have been current. One, as advanced by 

 Brauer ('93), is that each quadruple chromosome originates by 

 a double splitting of each chromatic element, i.e., by two longi- 

 tudinal divisions of each chromosome. The other, advanced as a 

 theory by Weismann, and since demonstrated by Ishikawa ('91), 

 Haecker ('93), vom Rath ('92), Henking ('91), and most ably by 

 Ruckert ('93, '94), is that the " Vierergnippeji'' originate by two 

 divisions of the chromosomes, the first being longitudinal, the 

 second transverse. 



According to my conception the origin of the " Vierer- 

 gnippen " in Liivibricus is quite different from either of the 

 above. It is as follows : there is indeed a horizontal division 

 (Fig. 12) (shown by the double spirem), and later a transverse 

 division, but this gives thirty-two double instead of sixteen 

 quadruple chromosomes ; the " Vierergr?ippen,'' or quadruple 

 chromosomes, are formed later by union of these double chro- 

 mosomes two by two. In the forms examined by Ruckert 

 sixteen double chromosomes are formed ; these are arranged 

 in a nuclear plate and transverse division takes place while in 

 this position, thus forming the " Vierergriippen." 



