578 REPORT—1905. 
of the odspore. It is possible that it may have something to do with the forma- 
tion of oil, which appears in such abundance in the ripe odspores. It begins to 
disappear just at the time the oil begins to form. The oil at this stage is only 
present in small drops, but soon after its disappearance a large quantity of oil 
appears. It is well known that fats, as well as other non-nitrogenous bodies, may 
appear as decomposition products of proteids. There is nothing, therefore, to 
preclude the possibility of the coenocentrum being associated with the formation 
of the fatty substances of the odspore. Some phenomena which have been 
observed by me in the maturation of the zygote of Polyphagus support this view. 
After fertilisation has taken place the two nuclei, although they come into close 
contact, do not fuse, but separate to opposite sides of the cell. They are large 
and prominent at this stage, but they gradually become smaller, and a part of the 
nucleolar, or, as it is in this case, the chromatin contents, become extruded into 
the cytoplasm to form a granular mass around each nucleus. The two nuclei 
then approach again, and the two masses of nucleolar chromatin become united in 
the centre of the cell to form a large spherical mass of deeply staining granules, 
with the two nuclei, which are now very smal], embedded in it. It is probable 
that this body is of the same nature as the ccenocentrum. It stains deeply in 
hematoxylin, and it also gives a strong reaction for phosphorus, which indicates 
its nuclear origin. It soon begins to disappear, and in place of it we find an 
irregular globular mass of oil or oil globules. 
From a consideration of these facts it seems to me far more likely that the 
function of the ccenocentrum is connected with those metabolic activities of the 
zygote, which must at this stage in its development be very considerable, than 
with the exertion of an attractive influence upon the sexual nuclei. It is difficult 
to see how such a selective chemotactic stimulus could be exerted as to act upon 
one nucleus only out of the large number in the odgonium. But the evidence 
before us does not admit of any definite solution of the problem at present. The 
subject demands further investigation of such a kind that a comparative study of 
the formation and disappearance of the cosnocentrum, the formation of the oil 
reserves, and the changes in the nuclei, should be carried on side by side. 
The Nuclei of the Lower Plants. 
The presence of nuclei in the algz and fungi had already been recorded by 
Niageli and many other observers shortly after the discovery of the nucleus by 
Robert Brown, but it is doubtful whether all the structures described as nuclei 
by these early observers were really so. It is only in comparatively recent times 
that it has been possible to determine with any degree of certainty that the minute 
deeply stainable bodies described more especially by Schmitz (1879) could be 
regarded as nuclei. This determination was easily made for many of the alge, 
especially by the researches of Strasburger, who described both the structure and 
mode of division. But among the fungi the structure and mode of division of 
the nuclei were practically unknown twenty years ago, and we have the opinion 
expressed by De Bary in 1887 that the satisfactory discrimination of true nuclei 
from other small bodies contained in the protoplasm can only be obtained after 
renewed investigation. 
Previous to 1887 cases of karyokinetic division in fungi had been described by 
Sadebeck (1883), Strasburger (1884), Fisch (1885), and Hidam (1887). Hartog 
(1889) described a process akin to karyokinesis in the Saprolegnies, and at the end of 
that year a true process of karyokinesis was shown to occur in Peronospora, Since 
that time our knowledge of the process of nuclear division in the fungi has been 
largely extended, and the phenomenon has now been found to be of general 
occurrence in the group, and many of the forms are unusually favourable objects 
for the study of the process. 
The only groups of plants in which true nuclei haye not been found are, so 
far as I know, the bacteria, Cyanophyces, and the yeast fungi. In the yeast 
plant there is a large homogeneous spherical body which gives the reactions of 
chromatin similar to the chromatin of true nuclei. With this is associated a 
