Reed . — The Nature of the Double Spireme in Allium Cepa . 275 
To return to the prophases. When the sixteen chromosomes have 
been organized they pass on to the equatorial plate, and there they are 
seen to be arranged in pairs (PL XVIII, Figs. 16 and 17). The pairing is 
suggested not only by the approximation of the chromosomes, but also by 
the fact that members of a pair often show a similarity of form and size. It 
is not always possible to make out eight distinct pairs, but this is probably 
due to the fact that some of them lag behind the others in taking up their 
position, and that they are seen from different angles. Further, it seems 
probable that the members of a pair are both derived from the same sub- 
division of spireme (Pl. XVIII, Figs. 10, i<5, 17). Muller (16) has recently 
shown that a similar pairing of chromosomes takes place in Yucca, but only 
among the larger chromosomes. Gregoire (8) denies the existence of paired 
chromosomes for A. Cepa. Gates (6) and Strasburger (22) have also 
described pairing of chromosomes in Oenothera and Pisum respectively, and 
Stomps (21) in the somatic nuclei of Spinacia oleracea. 
Metaphase. 
Details of the method of attachment of the chromosomes to the spindle 
fibres have not been followed. 
The chromosomes become V-shaped or form loops with one longer 
and one shorter arm. 
Gregoire (8) states that they become attached by their bent parts, and 
that these are the first parts to separate. This is undoubtedly a common 
occurrence, but the ends sometimes separate before the middle parts 
(PL XVIII, Fig. 17). 
PL XVIII, Figs. 17, 18, 19, 20, 21, and 22, show the separation of the 
daughter chromosomes. It will be noticed by a comparison of the figures 
that the split previously observed in the prophase is the one which now 
brings about the separation of the daughter chromosomes. 
Sometimes the longitudinal split closes up during the later stages 
of prophase, and it should be noticed that when this is the case the 
re-formed split shows first of all as a series of vacuoles which gradually 
fuse and effect the separation of the daughter chromosomes (PL XVIII, 
Figs. 2i, 22 a). 
Anaphases. 
As the daughter chromosomes pass to the poles they retain their 
V- or loop-shaped forms ; they seldom appear to be straightened out in the 
passage to the poles of the spindle. 
During the separation of the chromosomes the arrangement in pairs 
still remains evident (PL XVIII, Figs. 23 and 24). It should further be 
noticed that the members of a pair are very similar in form. The pairing 
cannot be seen amongst the whole sixteen chromosomes, but this is probably 
