19 ARTHUR BOLLES LEE 
they say ‘ achromatic’). It stains energetically in the fresh 
state with acid methyl green ; and in the fixed state it stains 
energetically and selectively with safranin, gentian violet, 
and the other usual basic stains. The only ground that I 
can discover for the belief in an ‘achromatic’ core in it is 
the fact discussed above, that the periaxial spiral generally seems 
more darkly stained than the rest of the eylinder round which 
it winds. But that does not in the least pomt to a difference of 
chromatophily between the two. The mner part of the axis 
stains (generally) less darkly than the spiral because it is less 
dense. And that is all; for the two stam, qualitatively, with 
exactly the same selectivity for stains. 
The sheath isa continuous tubular membrane, of a thick- 
ness of the order of about one-twentieth of a micron. It is of 
irregular calibre, but roughly of a diameter of about three times 
that of the axis (see figs. 2 to 18 and others). It is very fre- 
quently seen to be indented where the lateral processes insert 
on it, as though it were held down at these points, but blown 
up between them. It is sometimes seen to be continued round 
the tip, as in most of the figures given; but sometimes seems 
only to reach to the base of the dome-like surface, as in fig. 14. 
It is absolutely structureless. Itis decidedly acidophilous, 
staining readily though somewhat feebly (to about the same 
degree as spindle fibres, for imstance) with Saurefuchsin, 
Saiureviolett, or Lichtgriin ; and not staining with basic dyes. 
The space between this membrane and the axis is filled with a 
substance of glassy clearness, which is free from all trace of 
eranules or other differentiations, and entirely achromatic, 
not staining in any way. If it appear to be tinted, as it some- 
times may, that is due to the staming of the membrane. This 
substance may be liquid, or may be gelatimous. 
I find the sheath on all anaphase chromosomes of which 
I can obtain sufficiently good images ; and have concluded that 
it is as universal an attribute of all chromosomes of this stage 
as the axis and the periaxial spiral. 
These, then, are the features which can be detected on 
favourable specimens of animal chromosomes at the anaphase. 
