510 Wager . — On Nuclear Division 
of the specimens, owing to some change in the resistance of 
the basidium to contraction consequent upon the passage of a 
considerable quantity of protoplasm into the spores which 
might also affect the nuclei. Or it may be that the nuclei 
take up this basal position in order to facilitate the entry of 
protoplasm into the spores, and their apparent fusion in this 
position may be simply an incidental phenomenon consequent 
on their being brought into such close contact with each other 
in the narrow basal portion of the basidium. But these are 
only suggestions and perhaps other observers may be able to 
explain the phenonemon more clearly. 
The protoplasm of the basidium now becomes less dense 
owing to the transference of a large quantity of it into the 
spores which during this time have been increasing very much 
in size. The nuclei at the same time reach the apex of the basi- 
dium and so arrange themselves that one nucleus lies at the base 
of each of the sterigmata (Fig. 30). This does not take place 
in A. stercor arms until the spores have reached their full size 
and have become surrounded with a thick brown wall, but in 
A. muscarius it takes place before the spores have become 
fully developed and while the wall of the latter is yet very thin. 
The structure of the nuclei is at this stage quite normal. Each 
consists of a nucleolus which stains dark purple, a nuclear 
network which stains light blue, and a nuclear membrane 
which stains nearly the same colour as the nucleolus. They 
are best seen in transverse sections of the basidium. Soon 
a change appears in each nucleus, preparatory to its entrance 
into the spore ; the outline becomes irregular and the nuclear 
membrane more indistinct ; at the same time the nuclear 
network loses its definite appearance and becomes a somewhat 
homogeneous mass difficult to distinguish from the protoplasm 
immediately surrounding it ; the nucleolus becomes smaller, 
so much so that it is difficult to differentiate it from the 
refringent protoplasmic knots which are found at this stage in 
the basidium. Then, in some way which I have not been able 
to make out clearly, the nucleus makes its way through the 
opening of the sterigma into the spore, where it immediately 
