in the Hymenomycetes . 509 
appear as if fused together into a homogeneous mass, in which, 
however, the four nucleoli can still be made out (Fig. 28). 
Whether this is a true fusion or not I could not satisfactorily 
determine. That some change takes place is seen in the fact 
that the network of the nuclei in this condition becomes more 
deeply stained and thicker than before and the nuclei them- 
selves appear to become contracted. 
While this apparent fusion is going on, the spores begin to 
form at the apex of the sterigmata, and before they are fully 
formed, the four nuclei begin to separate from each other again 
(Fig. 29). As this takes place, the nuclei are seen to be extremely 
irregular in outline and to possess what appears to be a very 
thick nuclear membrane. This apparent thickness of the nu- 
clear membrane is due, however, so far as I can make out, to 
the irregularly coiled thick nuclear threads which have taken 
up a position at the periphery of the nucleus, and when seen in 
optical section present the appearance of a thick membrane 
surrounding the nucleus. The ordinary nuclear network, in 
fact, seems to have disappeared with the exception of a few 
very slightly stained delicate threads which traverse the cavity 
of the nucleus. The nucleolus in each case is in close contact 
with the thick peripheral thread at this stage. As the 
nuclei separate still further from each other, they gradually 
expand and assume a spherical outline. Then they begin to 
move upwards towards the apex of the basidium, and, as this 
takes place, they gradually regain their former structure and 
soon present the appearance of normal nuclei with the same 
staining reactions as they originally possessed. It is difficult 
to understand the meaning of this curious phenomenon. The 
fact that, at the moment when the nuclei begin to separate 
from each other, they present a very much contracted appear- 
ance, leads me to suppose that there is no real nuclear fusion 
but that the production of this confused irregular mass at the 
base of the basidium is due to the contraction of the nuclei 
and subsequent alteration in some way or other of the nuclear 
network. It may be an effect produced at a certain stage by 
the action of reagents used in the hardening and preparation 
