584, REPORT—1905. 
In the simplest case the cell of Beggiatoa contains only cytoplasm witl- 
out, so far as I can see by careful examination with the highest powers available, 
any differentiation of chromatin grains or structures of a like nature. Neither doI 
think that we can regard the protoplast as representing a nucleus. As Fischer 
points out, the idea that the protoplast of the bacteria stains like a nucleus is not 
correct, and, as I have been able to show, it certainly does not give a phosphorus 
reaction like a nucleus. It is, in fact, a simple undifferentiated mass of cyto- 
plasm, either homogeneous or at times exhibiting a foam structure. In this 
cytoplasm a few granules of chromatin may become differentiated, and this is the 
first indication of the separation of nuclear substance. Whether there are any 
species of Beggiatoa or other bacteria which are permanently without nuclear 
granules I do not know, and it will be very difficult to prove it; but the fact that 
under certain conditions these cells exist without them seems to point to the con- 
clusion that this may be the primary cell structure, as has been surmised by Haeckel 
and others. 
At an early stage in the evolutionary history of the protoplasm, before a 
typical nucleus was evolved, we appear to have had the development of colouring 
matter for the function of assimilation, and a bifurcation into the two distinct 
lines of descent of the fungiand the alge. This appears to have been accompanied 
by two distinct lines of nuclear evolution leading respectively to the development 
of the central body of the Cyanophycee and the nuclear apparatus of the yeast 
plant. The possible lines of development of the nucleus up to the yeast fungi on 
the one side and to the Cyanophycee on the other are clearly indicated in the 
diagram ; but between the yeast fungi and the true fungi, and between the Cyano- 
phycesw and the alge, there are gaps which we cannot bridge at present. 
It is possible that the evolution of the typical nucleus may have been brought 
about in the fungi by the more definite association of the nuclear vacuole with 
the homogeneous nuclear body, possibly acccompanied by a vacuolation of the 
latter, or that the nuclear body itself may have become the nucleus direct by a 
process of vacuolation and differentiation within itself. 
In the case of the Cyanophycee I have already shown that the central body is 
a vacuolar structure associated with granules of chromatin, and that sometimes 
this vacuolation becomes so pronounced in resting cells that we get an appearance 
as of a limiting membrane between it and the cytoplasm. The granules run 
together and become associated in such a way as to simulate the spireme thread 
of an ordinary nucleus. Further, we have in some Cyanophycev a differentiation 
of a nuclein-like substance in the form of the red granules of Butschli at the 
periphery of the central body, which may be an early stage in the separation of a 
portion of its substance to perform the special functions of the pyrenoid. The 
complete separation of this into a definite pyrenoid and the formation around the 
remainder of a nuclear membrane would give us a differentiation comparable to 
some extent to what we find in Euglena viridis, where we have a reticulate 
nucleus which divides by a rudimentary process of karyokinesis, in which, so far 
as we know, there is no definite formation of chromosomes and no longitudinal 
splitting. 
As to when or how the higher differentiation of the nucleus, with its 
chromosomes, longitudinal division, and spindle figure, arose we do not know. 
Possibly a careful investigation of the lower forms of the fungi and alge and 
such organisms as Euglena, and especially the protozoa, may throw light upon 
this difficult problem. 
