2) 
THE STRUCTURE OF TRYPANOSOMA LEWISI. 775 
the conclusions to which I come further on in this memoir 
with regard to the minute structure of this body in Try pano- 
somalewisi. The trophonucleus is a rounded oval body with 
a distinct limiting envelope, which is not to be regarded as a 
true nuclear membrane in the sense in which this term is 
used for metazoan nuclei, but, in all probability, as a con- 
densation at the periphery of the chromatin-substance itself. 
Inside tlis envelope is a space, filled doubtless in the living 
animal by a nuclear sap, in which are contained other chro- 
matin-bodies ; first of all the conspicuous karyosome, some- 
times double or further subdivided, which in its staining 
reactions resembles the kinetonucleus, and appears of dense 
texture ; secondly, smaller granules of chromatin, some of which 
may be fairly large and plainly visible, but which for the 
most part appear to be minute and not capable of being 
resolved by the microscope as distinct structures, but are 
scattered in a state of fine division throughout the nuclear 
sap, giving to the trophonucleus the even dark grey tint 
which it shows in an iron-hematoxylin preparation at a 
certain degree of extraction, or the pale red tint which it 
exhibits after Twort’s stain. 
Applying the conclusion stated above, namely, that the red 
stain of the Romanowsky mixture deposits round the struc- 
tures it stains, to the conception of the structure of the 
trophonucleus that I have put forward, we can explain the 
results of the stain as follows. The deposition of the stain 
round the nuclear membrane accounts for the apparent 
increase of size of the nucleus as a whole. At the same 
time the stain is deposited round the minute granules of 
chromatin within the nucleus, enlarging them to relatively 
coarse grains. ‘The karyosome doubtless shares also in the 
enlargement, but is generally obscured by the closely packed 
and secondarily enlarged chromatin grains, and is con- 
sequently very difficult to make out clearly. 
In support of the above conclusion I refer to the series of 
figures drawn from three preparations (a, b, c) which were 
made at the same time from the same rat, and which wereall 
