SOMATIC CHROMOSOMES IN VICIA 3oi 



superposed at the point of insertion, a point emphasized by Grégoire 

 (12) in a criticism of the work of Dehorne (ii), who has overlool^ed thèse 

 stages, and represents the chromosonnes with the halves side by side and 

 not in actual connection with the spindle. Lundegârdh (12 c) states that 

 some of them may not be in superposition, but the présent writer finds on 

 the contrary that they are always so placed. This arrangement seems to be 

 a necessary stage preceding the séparation of the halves. 



The points of insertion of ail the chromosomes lie in a single plane, a 

 feature not shown in fig. 22, since this figure represents a cell eut obliquely 

 and selected to illustrate the superposition of the halves rather than the 

 arrangement in a single plane. The latter point is shown in several of the 

 following figures of the anaphase. The insertion of the fibers may be at 

 any point on the chromosome. In fig. 22 it is at the end, in fig. 24 and 

 27 the long chromosomes are inserted at their middle points, and an inter- 

 mediate position is shown by the lower chromosome in fig. 25. This stands 

 in agreement with Grégoire's (12 results on Galtonia, Alliiiin and Trillium. 

 B0NNEVIE (11) reports a médian insertion in Alliiim, while in Vicia Fraser 

 and Snell (ii) describe an end insertion, which is surely the most fré- 

 quent. 



In Salamandra and Alliiim Dehorne (11) shows the double chromo- 

 somes arranged in pairs at metaphase, a phenomenon also reported by 

 Gates (12) for Oenothera. Lundegârdh (10) dénies the existence of such 

 a pairing in Allium and Vicia. The présent writer has also failed to find 

 évidence for it in Vicia. Occasionally one or two « pairs " may be obser- 

 ved, but this is held to be purely fortuitous. 



In préparations which comparative study shows to be well fixed the 

 spindle appears as a very weakly developed structure. Its limits are made 

 out with great difficulty or not at ail. The greater density of the -^ fibers - 

 where they are attached to the chromosomes and the small projections on 

 the latter at thèse points, fig. 22-26, give a strong impression of bundles 

 of fibers actually puUing the daughter chromosomes apart. It is évident, 

 however, as many writers hâve pointed out, that this simple interprétation 

 can no longer be applied, and that the spindle should be regarded as a ré- 

 gion of streaming or other activity along which the chromosomes move, and 

 which is so altered by the fixing agents as to become more distinctly 

 fibrous and visible. This is emphasized by the fact that in Vicia the 

 poorer the gênerai fixation the more clearly the spindle fibres stand out, as 



