504 Wager. — The Nucleus of the Yeast-Plant. 
was unable to confirm the observations of Hieronymus, al- 
though he used the same methods and the same appliances, 
but was able to demonstrate the nucleus by the use of 
Merkel’s solution and subsequent staining with fuchsin and 
methylene-blue. He did not complete his investigations, 
however, owing to the appearance of Janssens’ paper. 
Janssens (’93) states that not only do the cells of Yeast 
contain a nucleus, but that in the process of budding and 
spore-formation it divides karyokinetically, and the author 
was able to observe some stages of this, including the spindle- 
figure. He examined various Yeasts, including S. Cerevisiae 
and S. Ludwigii , to which he paid special attention. The 
nucleus possesses a nuclear membrane and a nucleolus. The 
latter is about one-third the diameter of the nucleus, and is 
homogeneous. In spore-formation the nuclear wall disappears 
from around the nucleolus. The first karyokinesis takes place 
longitudinally in Y. Ludwigii , transversely in 5. Cerevisiae I. 
The diaster and equatorial plate are easily seen. The second 
karyokinesis completes itself perpendicularly to the first, and 
the two spindles have a perpendicular direction to one 
another. The spores contain one nucleus, which becomes 
especially clear if the cells are placed during germination in 
water to which a little wort has been added. 
Dangeard (’93 and ’94), from a study of material which had 
been fixed by alcohol and stained with haematoxylin, also 
affirms that a distinct nucleus is present. The nucleus is 
placed in the layer of protoplasm surrounding the central 
vacuole. It is spherical in shape, possesses a thin membrane, 
and a large nucleolus which takes up the stain strongly. The 
process of division of the cell takes place by the formation of 
a bud on that side of the cell diametrically opposite to the 
nucleus. The nucleus passes to the point of attachment of 
the young bud and undergoes division which, according to 
the author, is in most cases direct. One-half then passes 
into the daughter-cell. No membrane is visible round the 
nucleus while this is taking place, but as soon as it comes into 
the daughter cell it develops the ordinary structure. 
