TRANSACTIONS OF SECTION K, 579 
prominent vacuole which contains a more or less amorphous substance of a 
chromatin nature. The two appear to be very closely related and undergo division 
simultaneously. From a study of the reactions of these two structures and 
their behaviour during division and in the formation of spores I suggested some 
years ago that the two together represent the nucleus of the higher plants, and 
therefore might be regarded as the nuclear apparatus. Guilliermond shortly 
afterwards in an exhaustive memoir tried to show that the homogeneous body 
described by me was a true nucleus with a normal nuclear structure, and that 
the nuclear vacuole, as I called it, must be simply an ordinary vacuole containing, 
however, a deeply stainable substance which he calls meta-chromatin. It is true 
that in most cases observed by him the nuclear body was perfectly homogeneous, 
but he accounted for this by stating that the fixing and staining had been 
imperfect. I have recently investigated a large number of different varieties 
of yeast with the result that my views as to the structure of the nuclear apparatus 
have been confirmed and the importance of the nuclear vacuole emphasised. In 
one case of a yeast which had been placed for some time in a sugar solution I 
discovered a structure in the nuclear body of the nature of a vacuolation which 
might be easily mistaken at a superficial glance as a normal nuclear structure. 
This structure or vacuolation, however, is closely connected no doubt with modifi- 
cations in the activity of the cell due to a different nutrition, and may be con- 
cerned with the changes leading to spore formation in which, as I previously 
showed, the nuclear apparatus becomes modified, the vacuole disappearing and 
the nuclear hody becoming more granular. I have, in fact, been able to obtain a 
complete series of stages showing the progressive modifications in the nuclear body 
leading to this condition, and am pretty clear that it is due to a process of 
vacuolation in the homogeneous body. 1 cannot agree with Guilliermond, there- 
fore, in his interpretation of these structures, although I do not doubt that the 
nuclear vacuole is nutritive in function, and I do not object to his view that its 
contents are to be described as meta-chromatin. I am at the same time disposed 
to think that the homogeneous granule, which I have called the nuclear ody, 
may be the actual-representative of the nucleus, the vacuole being looked upon 
as merely serving a nutritive function for the nucleus. In that case we have a 
very simple nucleus indeed, but one which is of importance in helping us to 
arrive at conclusions concerning the nature of the nucleus in the bacteria and 
Cyanophycess. 
The Cell Structure of the Cyanophycee. 
It is easy to demonstrate in the living cell of the Cyanophycee that the contents 
are differentiated into two distinct regions: (1) an outer layer containing the 
colouring matter; and (2) a central colourless portion which is known as the 
central body. The central body is considered by many investigators to be a true 
nucleus. It contains a deeply staining granular substance which to some extent 
resists the action of digestive fluids, and is therefore similar to the chromatin in 
the nuclei of the higher plants. In 1887 Scott was able to demonstrate a reticulate 
structure in this body, and slso saw some indications during its division of a 
process akin to karyokinesis. Zacharias also in the same year, largely on micro- 
chemical grounds, concluded that it was a nucleus. The problem has been the 
subject of investigation by numerons observers since that date with very varying 
results. These results may be shortly summarised as follows: The central body 
is not a nucleus (Macallum, Fischer, Massart, Chodat). It is a nucleus of a simple 
or rudimentary type (Hieronymus, Nadson, Butschli). It is a true nucleus similar 
to that found in the higher plants, and forms both chromosomes and spindle (Hegler, 
Kohl, Olive, Phillips). 
The facts of the structure of this body, so far as I have been able to ascertain 
them by the examination of the cell both in the living and fixed conditions, are 
that it possesses a vacuolate structure, associated with granules which stain deeply 
in nuclear stains, resist the action of digestive fluids, give a strong reaction for 
phosphorus and masked iron, and, further, according to the recent researches of 
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