Notes. 
763 
There is thus in these two cases an exact parallel to the behaviour 
of Zygosaccharomyces during spore-formation, and there can be very 
little doubt that a sexual act takes place here, as in the case already 
described by the author of the present communication. Having 
regard to the irregular forms of spore-containing cells of such species 
as Schizosaccharomyces mellacei and S. Comesii , which closely resemble 
the spore-containing cells of S. Pombe and Zygosaccharomyces , it seems 
very probable that in these cases also conjugation takes place as 
a preliminary to spore-formation. 
In the three cases of conjugation which have now been observed, 
there seem to be suggestive modifications of the process. In Zygo- 
saccharomyces the ultimate shape of the compound cell remains the 
same as it is found immediately after conjugation ; i. e. two more or 
less ovoid cells joined together into one compound cell by a con- 
spicuous neck or bridge, which under certain conditions can be made 
to grow out to some considerable length. In S. Pombe , while the 
compound cell has a similar form to that in Zygosaccharomyces , in 
some cases it loses this structure, being modified so as to appear 
as a rather enlarged ovoid cell. In S. octosporus the latter is the 
usual occurrence, all traces of the two individual cells being lost. 
Moreover, in this species conjugation does not always seem to occur, 
a single cell becoming an ascus without any conjugation with another 
cell. In the light of these facts, Janssen and Leblanc’s observation 
on the division of the nucleus of the spore mother-cell into two nuclei, 
and the subsequent fusion of these previous to the series of divisions 
which yield the nuclei of the spores, becomes very interesting. If 
Guilliermond’s statement, that Wager’s e chromatin-containing vacuole’ 
is not a part of the nuclear apparatus, be correct, then the latter’s 
interpretation of the fusion described by Janssen and Leblanc cannot 
suffice. It is true that Guilliermond has not observed such fusions, 
but he evidently does not consider that that fact proves that they 
do not occur, for he proposes to investigate the point specially. 
A confirmation of Jannsen’s and Leblanc’s observations would throw 
considerable light on the question of spore-formation among the 
Saccharomycetes , strongly supporting the hypothesis that it is a very 
much reduced sexual act. The gradual reduction or degradation 
of this act is traceable through the forms described above. In 
Zygosaccharomyces , independent cells fuse, retaining their indi- 
viduality after fusion. In S. Pombe this is also usually the case, but 
