8 ARTHUR BOLLES LEE 
especially 14 ; and at this point is generally somewhat flattened. 
At its ends (where not sectioned by the knife) it terminates 
in a smooth dome-shaped surface, from the summit of which 
there can frequently be seen to emerge a tiny tag, the vestige of 
its union with its late sister chromosome, figs. 6, 7, 14, 5, 12, 
all of which show the tag; and 3 and 4. It is undoubtedly 
solid, not hollow. Surface views (see the figs. quoted) show no 
lumen, nor any trace of the alveoles found in plant chromosomes ; 
but they may seem to show a border darker than the innermost 
part, as in one or two of the chromosomes of figs. 8, 4, and 5. 
But in these cases it is generally possible to see that this border 
is not continuous, but consists of a series of elongated dots. 
Transverse sections frequently show as disks with a dark 
border and lighter centre, fig. 15, which may give rise to the 
impression that there exists an axial lumen. But I have satis- 
fied myself that the axis is in reality solid, and that the dark 
border is due, for the most part at least, to the periaxial spiral, 
about to be described, showing there. It is frequently pos- 
sible, by very careful focusing, to see that this border is darker 
at one side of the disk than the other, which I take to be due 
to a sector of the spiral being in sharpest focus there. Thus in 
fig. 15 a, at the top left it is darker to the right ; at the top right, 
darker at the bottom ; and in the lowest disk darker at the top. 
And the darker sector can be seen to turn round the disk with 
every change of focus ; which is just as a spiral viewed end-wise 
must behave.’ Similar images are shown, more clearly, by three 
of the less darkly stained chromosomes of fig. 15¢. Those of 
fig. 15b show the darker border as an apparently entire ring, 
not a mere sector; and the fourth chromosome of 15¢ shows 
as a disk with a mere hint of a darker border. 
Further, in the lighter-coloured centre of the disk there can 
sometimes be seen a darker comma-shaped dot. One of these 
is Seen as a mere dot in the two upper disks of fig. 15 a, and as 
! For this spiral to be demonstrated it is imperative that the chromosome 
be not overstained, for if it is the axis will appear as dark as the spiral, and 
the spiral will not be seen. Vejdovsky’s figures grossly exaggerate the 
distinctness of the spiral at the best of times. 
