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show a somewhat different nuclear picture. Instead of the irregular 
red staining mass which often is produced into strands, evidently the 
result of drying and partial flattening on the slide, the nucleus is made 
up of a group of deeply staining (Heidenhain’s iron haematoxylin 
method) masses of chromatin. The masses appear to be bound together 
by a paler reticulum. The masses of chromatin are so closely packed 
together that it is often difficult to make out any further structure. 
If, however, the differentiation in the iron alum solution is carried 
further, it will be found that the deeply staining masses become dis¬ 
coloured and that some further details can be detected. The nucleus 
will then be seen to consist of a ring of minute granules at the centre 
of which is a larger granule or karyosome. This is evidently an optical 
section of a vesicular structure. It is difficult to say if any definite 
nuclear membrane is present or not, but the regular arrangement of the 
granules in a ring suggests a nuclear membrane. I am inclined to the 
view that a definite membrane is present. Within the membrane between 
it and the karyosome can be seen some very fine granules. The nucleus 
of this haemogregarine is then a vesicular nucleus limited by a nuclear 
membrane on the surface of which in deeply stained specimens large 
staining masses obscure all other structure, while in more discoloured 
specimens the nuclear membrane is seen to be covered with small 
granules. At the centre is a definite karyosome, surrounding which 
are still fewer granules arranged on the nuclear reticulum. 
Reproduction in the spleen and hone marrotv. 
It has generally been supposed that this haemogregarine reproduces 
almost exclusively in the bone marrow, but in the case of the Bagdad 
dogs, at any rate, the reproducing forms are found as commonly in the 
spleen as in the bone marrow. 
The reproduction follows two distinct lines. In one case, and this 
is the method which has hitherto been described, the resulting products 
of reproduction are numerous small bodies resembling the haemo- 
gregarines found in the leucocytes in the peripheral blood (PI. XVI, 
fig. 8). In the other case, not described previously, the products of the 
reproduction are much less numerous (generally three) and very much 
larger, reaching a length of 15 p (PI. XVI, figs. 3 and 6). It may be 
stated at once that the small bodies are destined to enter the leucocytic 
cell in the peripheral blood, and that they are most probably gametocytes 
