800 E. A. MINCHIN. 
secondly, that when the Romanowsky stain is cautiously 
extracted the nucleus comes down to a condition similar to 
that seen after other stains (figs. 68, 69). 
The parts of the trophonucleus may be considered under 
the heads of the “membrane,” the “ karyosome”’ or “karyo- 
> and the ‘‘intra-nuclear chromatin,” the latter term 
somes,’ 
being understood to be exclusive of the karyosome. 
The membrane appears as a faint but distinct line circum- 
scribing the oval contour of the nucleus. It does not, however, 
stand out sharply from the contents, nor does it stain a 
different colour from the rest of the nucleus; it also never 
shows a double contour. For all these reasons the membrane 
may be regarded simply as the superficial limit of the intra- 
nuclear chromatin, condensed to form a more closely knit 
zone at the surface. In other words, the membrane is not a 
true nuclear membrane in the sense in which the term is used 
for Metazoan nuclei. 
The karyosome appears usually as a single small grain at 
or near the centre of the nucleus ; this is the commonest con- 
dition, found in about 80 to 90 per cent. of the trypanosomes. 
I regard this, therefore, as the normal state of the nucleus, and 
will deal with it first, and describe afterwards other conditions. 
In order to see the karyosome clearly it is necessary to extract 
the stain thoroughly when staining with iron-hematoxylin, 
otherwise the karyosome is obscured by the granules of the 
intra-nuclear chromatin. The extraction should be carried on 
until the karyosome appears as a sharp, clear, and definite 
body. Wath ‘l'wort’s stain no such precautions are necessary, 
as the intra-nuclear chromatin does not take it up to the same 
extent, hence this stain is one of the best for showing the 
karyosome and the nuclear structure generally. In its re- 
actions the karyosome is very similar to the kinetonucleus, 
but stains less deeply and gives up the stain more readily. I 
infer from this that the karyosome is, like the kinetonucleus, a 
body consisting chiefly of chromatin on a basis of plastin, but 
that the chromatin is much less concentrated and condensed 
in the karyosome. 
