496 Wager. — On Nuclear Division 
division, than the former, in which the density of the protoplasm 
somewhat obscures this process. 
A basidium first appears as a small club-shaped branch 
projecting from the sub-hymenial layer. A quantity of proto- 
plasm passes into it from the hypha upon which it is borne. 
This may completely fill the basidium, or vacuoles may be 
present, especially at first. At a very early stage in the 
development of the basidium, two or more nuclei make their 
appearance in it. These appear to pass over from the hypha 
along with the protoplasm. The number of nuclei which thus 
make their appearance is two in A. stercorarius , two or three 
in A . muscarius and, according to Rosen, as many as six or 
eight in some other species. These nuclei are larger than the 
nuclei of the hyphae, and they may have arisen, therefore, by 
fusion of two or more of the latter during their entry into the 
basidium, or their larger size may be due to the superior 
nourishment to be obtained in the protoplasm of the basidium, 
as compared with that to be obtained in the hyphae. 
The structure of these nuclei can be very well made out at 
this stage (Figs, i, 2, 31, 32, 33). Each nucleus possesses 
a large deeply stained nucleolus, a very clearly defined nuclear 
network, in which a granular structure could be made out, espe- 
cially in A. muscarius, and a well-marked nuclear membrane. 
As the basidia increase in size, the primary nuclei, as 
we may call them, fuse together into a single large nucleus. 
I have been able to obtain sections showing all the stages of 
this fusion in A. stercorarius , so far as this can be ascertained 
in dead, stained specimens. Absolute proof that this fusion 
takes place depends perhaps upon the observation of living 
material, but this is impossible at present owing to the diffi- 
culty of observing the nuclei in the living state. The details 
of the fusion, as they were observed in stained specimens of 
A. stercorarius , are as follows: — The two nuclei gradually 
approach each other until they come into such close contact 
that a flattening of the two is produced where they touch each 
other (Figs. 3 and 4). A dumb-bell shaped structure is thus 
produced. The membrane separating the two nuclei now 
