582 REPORT—1905. 
may be embedded. As these granules stain deeply in nuclear stains, and also 
give a reaction for phosphorus, they are probably similar to chromatin. They 
are distributed throughout the whole cell, and are not specially confined to one 
lace. 
" The variation in size and number of the chromatin granules in the different 
species examined is very considerable. In the colourless Beygiatoa alba and in 
various Spirdla there are very few small granules. In some cells of Beggiatoa 
alba they appear to be absent altogether. In these cells there is, therefore, no 
constituent of the cell which gives a pronounced reaction for chromatin. The 
cytoplasmic network gives a very slight reaction for phosphorus, but this is so 
slight as to be of little value. 
In Bacillus subtilis there is one prominent granule, sometimes two, in each 
cell, and the same is true for B. anthracis according to Fischer, and for other forms 
of bacilli which I have observed. The structure of these bacilli is, in fact, very 
much like that of the yeast plant, except for the absence of the very prominent 
vacuole, of which, however, there is even here some evidence. 
The coloured bacteria, on the other hand, appear to contain an abundance of 
granules. In Beggiatoa roseo-persicina, the cytoplasm of which is coloured pale 
red, the granules are very prominent in the middle of the cell, and Fischer 
figures the same for Chromatiwm okenii. These granules stain deeply in 
hematoxylin, and give a fairly strong reaction for phosphorus, But there is no 
clear demarcation into a central body and peripheral coloured cytoplasm, as occurs 
in the Cyanophycee. 
We must conclude, therefore, that the bacteria do not contain anythiyg which 
can be individualised as a nucleus, but that the nuclein constituent of the cell 
when present is contained in granules distributed throughout the cytoplasm. 
Beggiatoa, and possibly other and more lowly forms, has under certain con- 
ditions apparently no chromatin granules at all. The cell contents give a slight 
reaction for phosphorus, if at all, and no deeper-stained granules can be clearly 
made out; the same result is obtained with methylene blue, and also with 
hematoxylin Under other conditions we find forms in which a few chromatin 
granules can be seen scattered about the cell, not in any special part of it nor in 
a central body. Hinze finds in a large form a considerable number of small 
granules. The cytoplasm exhibits a foam structure yery beautifully in some 
cases, but this appears to be mainly—I think not entirely—due to the spaces left 
by the sulphur granules. In some specimens with only a few such granules the 
comparatively thick strands of cytoplasm between the granules did not show any 
foam structure at all. 
The Evolution of the Nucleus. z 
All plant nuclei, from the alge and fungi upwards, present a striking 
similarity both in structure and mode of division. The same appears to be true 
of the animal kingdom, from the protozoa upwards. But among the protozoa on 
the animal side, and the yeast fungi, bacteria, and Cyanophycee on the plant side, 
there is a kind of border kingdom in which occur structures which appear to 
represent the nuclei of the higher organisms, but are so different from them in 
many respects that it is very difficult to say whether they should be regarded as 
nuclei or not. As we have already seen, the central body of the Cyanophycez 
and the chromatin granules of the yeast plant and bacteria may represent simple 
or rudimentary forms of nuclei. It is, therefore, possible that we may obtain 
from them a clue or indication of some kind as to the origin of the nucleus and 
the process of its evolution. 
It is among the protozoa that we find the greatest variation both in form and 
structure of these rudimentary nuclei. All the various parts of the nuclei of the 
higher animals can be recognised in them, but, as Calkins poivts out, are rarely 
resent in one and the same nucleus. Irom a consideration of the various types 
Calkins considers that the most primitive nucleus is probably a single mass of 
chromatin without membrane or reticulum. By the division of this into granules, 
