Wager . — The Nucleus of the Yeast- Plant. 533 
useful, but these two have given me the most satisfactory 
results. It is not easy to get satisfactory preparations, how- 
ever, owing to the difficulty of washing out the stain so that 
the cells are neither too deeply nor too lightly stained. 
In the process of spore-formation as seen in the living cell, 
the protoplasm first of all becomes filled with bright refractive 
granules, most of them exhibiting a Brownian movement 
(Figs. 34-40). The nuclear body can generally be very 
easily seen, and one vacuole only is present in most cells. 
Then the vacuole disappears, its place being taken by two or 
more smaller ones, which are still further subdivided until 
finally the protoplasm appears structureless, or in favourable 
specimens exhibits the foam-structure described by Butschli. 
The nucleolus at the same time moves towards the centre of 
the cell and is surrounded on all sides by the bright granules. 
A condensation of the protoplasm towards the centre or one 
side of the cell now takes place, and gradually the spores are 
separated out by a division of this protoplasm into two or 
more rounded masses, each of which becomes surrounded by 
a membrane and gradually ripens into a spore. 
From an examination of well-stained specimens, the changes 
which take place in the nuclear apparatus have been followed. 
Shortly after the Yeast-cells have been placed in the sugar- 
solution, the nuclear vacuole which contains a deeply-stained 
sphere or network of chromatin-like substance — the nucleolus 
of Janssens and Leblanc — begins to divide, first of all into 
two, then probably by further division into numerous smaller 
portions, until finally a delicate foam-structure of the proto- 
plasm is produced and the chromatin- substance becomes 
distributed through the protoplasm. The nucleolus is found 
near the centre or one side of the cell at this stage and is 
slightly less deeply stained than the protoplasm (Fig. 54). 
At this stage the nucleolus is very clearly seen, but in the 
earlier stages it is visible only after very careful staining. 
This has led Janssens and Leblanc to make, I think, a very 
curious but perhaps natural mistake. The primary division 
of the vacuole into two is described by them as the division 
