Wager. — The Nucleus of the Yeast- Plant. 515 
Species examined. 
The species of Yeast examined include — 
1. Saccharomyces Cerevisiae — obtained from Leeds breweries. 
2. Compressed Yeast — obtained from various agents in 
Leeds. 
3. S'. Cerevisiae — Hansen I. 
4. S. Ludwigii. 
5- S. pastorianus. 
6. A red Yeast found in the air of the Laboratory and 
cultivated on gelatine. 
7. S. Mycoderma. 
I am indebted to the kindness of Professor E. Chr. Hansen 
for Nos. 3, 4, and 5, and I take this opportunity of tendering 
him my thanks for the specimens he was good enough to 
send me. 
In order to make observations upon Yeast at different 
stages of fermentation, it was obtained fresh from a brewery ; 
the wort was drained off, and cultures started in Pasteur’s 
solution. In several series of investigations the Yeast was 
examined at the end of every hour, and specimens were fixed 
and hardened at the end of 1, 2, 3, 12, 16, 24, 38, 49, and 
72 hours. Observations were also made upon Yeasts kept in 
sugar-solutions of various strength and in distilled water, all of 
which afforded useful information. 
General Structure of the Yeast-Cell. 
The contents of the Yeast-cell vary according to the con- 
ditions under which it is placed. In fresh actively growing 
Yeast the cell-contents are generally clear and homogeneous, 
with perhaps one or more bright refringent granules. 
In young Yeast-cells and cells in an early state of fermen- 
tation-three or four hours in Pasteur’s fluid — a vacuole 
or vacuoles can be seen. Each vacuole contains at least 
one refringent particle which is in a state of movement, and 
