No. 5-] DESMOGNATHUS FUSCA. 20/ 



would be a qualitative, reducing division in the sense of 

 Weismann. No absolute decision between these two possi- 

 bilities could be arrived at ; nor does it seem to me likely that 

 a determination of the way in which the separation actually 

 occurs may be gained. 



I know of no results on other forms that furnish circumstan- 

 tial evidence in favor of a qualitative reduction taking place in 

 the manner suggested above as possible. Meves, it should be 

 remembered, found that in Salamandra the second division 

 was a qualitative equation division, and did not describe any- 

 thing corresponding to the X formation that occurs in Destnog- 

 7iatJius. 



The union of chromosomes, or daughter-chromosomes, in 

 pairs, whether with a reduction of the number one-half or not, 

 is conceded by most as furnishing a basis for a qualitative 

 reduction. Typically (perhaps) the reduction is accomplished 

 by the union in pairs of the chromosomes before the first split- 

 ting ; there being a reduction of the number to one-half and a 

 second longitudinal splitting being wanting; or (Calkins Mn 

 Linnbricus) conjugation may take place after the first longitu- 

 dinal splitting, and reduction follow, as in the typical case. 

 According to Lee,^ in Helix a longitudinal splitting of the 

 chromosomes, separation of the daughter-chromosomes, and a 

 subsequent fusion (so far resembling Korschelt's^ results on 

 OpJiryotrocJia) take place before the divisions of the spermato- 

 cyte, of which the first is longitudinal, the second transverse ; 

 there is thus no reduction in the number of the chromosomes, 

 but there is a quantitative and qualitative reduction in the sec- 

 ond division, the latter depending on the heterogeneous conju- 

 gation of chromosomes before the first division. 



If the second division in Dcsmognathus is to be looked upon 

 as a " reducing " division, it may be considered in two ways. 

 The original union of the chromosomes, after two longitudinal 

 splittings of the united chromosomes, is dissolved and a new 

 union between the daughter-chromosomes established ; or,. 



^ Journ. Morph. Vol. xi, pp. 271-302. 1895. 



2 La Cellule. Vol. xiii, pp. 201-270. 1897. 



3 Zeitschr.f. wiss Zool. Vol. Ix, pp. 543-688. 1895. 



