Some recent work on the cytology of fungus reproduction 
205 
they appear to agree with those in one of the unnamed species; the 
nuclei in the young zygospore, after dividing, fuse in pairs with the ex¬ 
ception of a few which degenerate. In the remaining species the nuclei 
are small and numerous and, as is usual, there is nothing to distinguish 
the nuclei coming from either gamete. All the nuclei except four degene¬ 
rate and these fuse two by two but not until much later than is usual 
in the other cases studied. 
Absidia Ovchidis is a species which is indifferently isogamous or 
heterogamous. It is however heterothallic. The nuclei are very numerous 
in the young zygospore. They fuse in pairs with the exception of a few 
which degenerate. Similarly with Mucor hiemalis another heterothallic 
and hétérogamie species, but here the nuclei are large in size and few in 
number and the fungus is therefore particularly suitable for study. The 
results obtained by Moreau seem fairly consistent. The facts brought 
out by his researches seem to be that in the Mucorineae there is a 
fusion of nuclei and a degeneration of nuclei. The variation depends upon 
whether the first or the second phenomenon is dominant. 
The deferred nuclear fusion in one of the Zygorhynchus sp. may 
be present only in heterogamous species but we have not yet sufficient 
facts upon which to base theories. It is interesting to note that the 
phenomena seem practically identical no matter whether the species is 
homothallic or heterothallic, isogamous or heterogamous. There is greater 
variation in the nuclear phenomena in Sporodinia grandis according to 
the various published accounts than is here recorded for eight different 
species. 
In the Ascomycetes the controversies have been much more severe. 
Apart from the older observers one has only to consider the work of 
Harper, Dangeard and Claussen on Pyvonema confluens to realise 
that we are at present far from having agreement as to the facts. 
In the Helvellineae , Carruthers (1911) has published a paper on 
Helvetia crispa. There is no ascogonium present in this species and in 
this respect it agrees with H. elastica (Me Cubbin 1910). Brown (1910) 
found an ascogonium in Leotia lubrica , although his specimens were too 
for advanced to work out its structure and development. This difference 
between the two genera is interesting as Boudier in his classification 
of the Discomycetes widely separates the Helvellaceae from the Leotiaceae 
on account of the method of opening of the ascus, the former being 
placed in the Operculés the latter in the Inoperculés. The data however 
is not yet sufficient to base any conclusions on, as we know that in the 
same genus even, an ascogonium may be present or absent e. g 
Humana where there is a well marked ascogonium in H. granulata whereas 
such a structure is entirely absent from H. rutilans. In Helvetia crispa 
the hypothecium is a loose tangle of hyphae with a variable number of 
nuclei in the cells. Certain of these nuclei where observed to fuse in 
pairs as in Humaria rutilans (Fraser 1908), but there was no evidence 
of nuclear migration such as occurs in that species. In H. elastica 
Me Cubbin found a very marked difference between fertile and vegetative 
hyphae, the former containing several nuclei in each cell, the latter only 
two. This exact differentiation between the two kinds of hyphae could 
not be traced in H. crispa although in most cases the cells of the para- 
physes are binucleate and the cells of the fertile hyphae multinucleate. 
