198 
H. M. WOODCOCK. 
nuclear material is c'lt times so sliarp aud well-defined that it 
might almost be regarded as a membrane. However^ now 
and again one is fortunate enough to be able to focus a definite 
line bordering the pale area in question on the outside^ which 
most probably represents a true nuclear membrane. And 
there are one or two other i-easous which support this view. 
Thus Siedlecki (loc. cit.) states that he observed this clear 
zone ill these forms of the para.site even in the living condition, 
which shows that, in the strained preparations, it cannot 
represent merely a shrinkage-space. Further, although this 
zone appeal’s so clear and pale by comparison with the 
parts of the parasite immediately suri’ounding, it is, never- 
theless, occupied by something — probably in the nature of 
nuclear sap — which is extremely faintly stained ; that this is 
actually the case is sometimes shown distinctly because of a 
peculiar condition or appearance which is often, but not always, 
presented by the karyosomes. These elements themselves, 
especially the larger ones, i.e. when there are only one or 
two, may be surrounded by a perfectly clear halo-like circle, 
which is quite colourless ; this halo round the karyosome 
passes between it and the central nuclear substance, indenting 
the surface of the latter, so that it forms a concavity or cup as 
it were. The difference between this small, quite colourless 
zone and the almost clear, faintly staining area, extending 
around the periphery of the whole nucleus is sufficiently con- 
spicuous. To sum up the matter, therefore, the kai'yosomes 
must be considered as really intra-nuclear, situated in a 
peripheral zone, which is very pale, and apparently consists 
only of nuclear sap, the rest of the nuclear material, con- 
taining a small amount of chromatin being aggregated to form 
a central mass. I have not been able to see any delicate 
threads or rays passing from this central mass to the limiting 
membrane of the nucleus, and traversing the faintly-stained, 
peripheral zone, nor does Jollos (loc. cit.) mention or 
figure anything of the kind; but Chagas (5) has described 
and figured “ liuiu threads,” having such a disposition in 
the case of somewhat older phases of a new species of 
