33i 
Centro spheres in Fungi . 
the functions of the nucleolus, viz. that of storing up the 
substance which causes the chromatic elements to stain red. 
The structure of the four daughter-nuclei in the basidium, just 
at the moment of their formation or shortly afterwards, is 
precisely similar to that of the hyphal nuclei. They possess 
a few chromatic elements stained red, but no nucleolus. As 
they increase in size, however, a nucleolus appears, and 
gradually the bright red colouring of the chromatic thread 
disappears and is replaced by the light or dark blue colora- 
tion which is found in the normal basidial nuclei. It appears 
as if in both cases the advent of the nucleolus caused the 
substance which produces the bright red staining of the 
threads to be given up, and if we regard the nucleolus as 
a storehouse of this substance, as appears probable from 
previous observations, we can, I think, understand more 
clearly the gradual formation of the nucleoli in the young 
primary nuclei of the basidium. 
The increase in size of these primary nuclei is probably 
due partly to growth, and partly to the fusion of nuclei. The 
nuclei appear to fuse together in £>airs, but I have not been 
able to follow this out satisfactorily. If such fusion does take 
place, it probably occurs both in the basidium and in the 
hyphae. But by whatever means the nuclei increase in size, 
a stage is at last reached when we have in the basidium two 
nuclei, each with a distinct reddish network and a single well- 
defined nucleolus which takes a reddish blue stain. No kind 
of archoplasmic body is visible at this stage. These two 
nuclei fuse together. I have seen them fusing, but have not 
been able to follow out all the details. At the same time 
similar nuclei pass into the basidium from the hypha and they 
also fuse together rapidly. The basidium now contains two 
nuclei, produced by the fusion of four pre-existing nuclei, and 
in contact with each nucleus, in some cases looking as if it 
were just being extruded from it, we can see a spherical body 
precisely similar to the nucleolus and stained in a similar way 
(Fig. 5). It looks exactly as if it were a nucleolus, the second 
one being extruded from the fused nucleus, and the fact that 
