638 Fraser . — The Behaviour of the Chromatin in 
figure (Fig. 20) ; and as they move, each arm of the U is seen to be longi- 
tudinally split (Fig. 21), so that the bivalent chromosome, which, viewed 
laterally, appears as a U form, is revealed when examined from the front, as 
two V's set base to base. Thus the longitudinal fission, lost sight of at the 
beginning of the second contraction, reappears upon the spindle. The 
chromosomes are attached to the spindle by their apices, and somewhat 
bulged out from it ; where they are much twisted, figures somewhat more 
complicated than those described above may be observed. 
The next stage is the separation of the two V-shaped sister chromo- 
somes. Generally one pair of ends is freed before the other (Fig. 22) ; the 
free limbs appear to contract somewhat, suggesting that the chromosomes 
are being pulled apart. Later, in the anaphase (Fig. 23), the limbs are 
usually of the same length. The longitudinal fission is always recognizable 
first at the end of the chromosome not attached to the spindle, and is never 
seen, at this stage, to reach quite to the attached end. 
It is instructive to compare the state of affairs on the heterotype 
spindle with that in the vegetative division. There also in Vicia Faba the 
chromosomes of the metaphase are attached to the spindle by one end, 
and there also the two halves of the chromosome move apart, so that 
a U-shaped or penthouse-shaped figure is formed. Only, in the vegetative 
division, this arrangement is due to the longitudinal split, and not, as in the 
heterotype, to the separation of whole premeiotic chromosomes. Conse- 
quently no further fission takes place on the vegetative spindle, and the 
chromosomes of the anaphase have the form of rods and not of V’s. 1 
Otherwise the mechanism of the two types of division is strikingly 
similar. 
The Homotype Division. 
When the chromosomes reach the pole of the spindle they become 
united one to another laterally (Figs. 25, 26), and sometimes also by their 
ends (Fig. 26), as in the somatic telophases, but without losing their 
V-shape. They do not produce a reticulum, and no satisfactory evidence 
of a new fission in their limbs could be obtained. After a brief resting 
period the cross attachments disappear, the chromosomes elongate con- 
siderably (Fig. 27), extending through the vacuole which has developed 
about them, and reach a stage which may be compared to the spireme 
of the vegetative prophases. Contraction then takes place, and they pass 
on to the homotype spindle, still retaining their individuality and their 
characteristic form (Fig. 28). 
The two homotype spindles may lie parallel (Fig. 29) or at an angle 
(Fig. 30) one to another, often one or both are curved (Fig. 30), and they 
1 A V-shaped chromosome in vegetative mitosis is due to the attachment of a bent rod by its 
middle, and is represented in the meiotic anaphase by a double V such as is found in Lilium. 
