STRUCTURE OF CERTAIN CHROMOSOMES 1] 
up or lower down, at the extremity of a line which prolongs the 
course taken by the spiral across the axis. This is shown in 
fic. 14; but in the remainder of the figures is not shown clearly 
on account of the frequent derangement of the symmetry of 
the disposition caused by stretching or other displacement of the 
sheath. But there can be no doubt that the relations of the 
two sets of cones are as described. 
The line that joins the elevations on the axis to the sheath, 
including its aponeurosis thereon, is very faint, but it can 
sometimes be seen to be stained. In that case, it stains in the 
same tone as the axis; for instance, I have obtained it un- 
mistakably red with safranin. This ligament, then, is a 
prolongation of the substance of the spiral. And, taking all 
these facts together, we must come to the conclusion that each 
of these apparently filiform ligaments is nothing but the optical 
section of a flange-like or pterygoid membranous ex- 
pansion of the spiral. This cannot be seen as a membrane, 
full face, because it winds round the axis in such a way as always 
to present its edge to the observer; and also because it is so 
thin (I should think anything under a twentieth of a micron) 
that if ever a portion of it should come to lie full face it would 
still be invisible through its thinness." 
We may, if we like, call the optical sections of this membrane 
lateral processes of the axis; which well describes the 
optical image. But then we must bear in mind that there 
is in reality only one of them, which courses continuously 
round the axis like the lamina spiralis cochleae round the 
modiolus. And we can make a rough model of a chromosome 
of this type by taking a carpenter’s screw and inserting it into 
a quill into which it will just fit. 
The whole of the chromatic axis, the iImmermost part as 
well as the spiral and the lateral processes, is most decidedly 
basophilous: no part of it is achromatic nor acidophilous 
(which is what the authors quoted in the Introduction mean when 
1 The aponeurosis of this membrane on the sheath can sometimes be seen 
as a spiral line running along the sheath.. I have abstained from drawing 
it on account of the difficulty of showing it clearly. 
