Wager . — The Nucleus of the Yeast- Plant. 529 
ditions contain chromatin-substance, recalls the structure 
observed in such cells as those of Spirogyra and perhaps 
the young cells at the apex of the root in Pkaseolus , in which 
much if not all of the chromatin resides in the nucleolus. 
We may I think therefore fairly conclude that the nuclear 
apparatus of the Yeast-plant consists of (1) a nucleolus, of 
homogeneous structure, the nucleus of the majority of previous 
observers ; and (2) a store of chromatin which may occur 
either (a) in a network enclosed in a vacuole in close contact 
with the nucleolus, or (b) in a network in direct contact with 
the nucleolus, or (c) disseminated through the protoplasm. 
The chromatin is under certain conditions taken up into 
the nucleolus, viz. in spore-formation, or in the later stages of 
fermentation when it seems to be very abundant in the cell. 
Further, if we regard it as a simple form of nucleus it 
may be either (1) a primitive structure representing an early 
stage in the phylogeny of the nucleus ; or (2) a degenerate 
nucleus such as might be the result of the degradation of the 
Yeast-Fungi from higher forms, as is usually supposed to 
be the case ; or (3) a special adaptation to the conditions 
under which the Yeast-plant lives and its rapid vegetative 
reproduction by budding. 
The latter alternative is supported to some extent by the 
phenomena which occur during spore-formation in the Hyme- 
nomycetes. In the basidia, when the spores are formed, four 
nuclei are present, each possessing the normal structure of 
a nucleus. But before they pass into the spores everything 
seems to disappear except the nucleoli, which are left free 
in the protoplasm at the base of the sterigmata. This sepa- 
ration of the nucleolus from the rest of the nucleus is probably 
a special adaptation due to the necessity of passing through 
the narrow neck of the sterigma into the spore ; and one can 
readily understand how valuable such an adaptation would 
be to the Yeast-cell with its very rapid vegetative repro- 
duction, and how likely it . is that such a condition of its 
nucleus should become a more or less permanent one as long 
as vegetative reproduction is unchecked. 
