ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
721 
than the first group ; they complete the fermentation, and, in the later 
stages, completely displace the apiculate forms. The third group also 
consists of ellipsoidal yeasts which, in a neutral or slightly acid must, 
behave rather like high yeasts, and acquire a rose or wine-red colora- 
tion ; they appear to have but little activity, but show marked power of 
sporulation during their most active period. 
Structure of Yeasts and their Development.* — The question 
whether yeasts have a nucleus or not has long been in dispute. 
M. P. A. Dangeard, from examinations of Ustilagineee, decides in favour 
of a nucleus which is constantly present, surrounded by a doubly con- 
toured membrane, and containing an evident nucleole. Abutting on 
the cell-membrane which encloses a thick layer of protoplasm lies the 
nucleus, so long as it is at rest. In the budding the nucleus plays a 
passive part. The young cell possesses a protoplasmic layer like the 
mother-cell, to which it is attached by a fine sterigma. The nucleus 
gets engaged in the passage to the new cell, and dividing, one part passes 
through the sterigma into the daughter-cell. The nuclear membrane 
and nucleole appear later. 
With regard to the systematic position of the Saccharomycetes, the 
author says that if his investigations upon the histology of the Usti- 
laginese support Brefeld’s views, it must be borne in mind that they 
do not controvert the conclusions which may be drawn from the pre- 
sence of spores in Saccharomyces. As to the appearances obtained by 
Hieronymus,! who instead of a nucleus found a central thread, the author 
regards them as due to insufficient fixation of the material. 
Action of Yeasts on Glycogen.f — Herren A. Koch and H. Hoseeus, 
who have been experimenting with yeasts on animal and vegetable 
glycogen, find that this substance exerts a markedly inhibitory influence 
on the production of alcohol. The glycogen was obtained from calves’ 
and rabbits’ livers, and from starch-free German yeast. The yeasts 
used in the fermentation experiments were brewers’ yeast, Frohberg 
yeast, and German yeast. The authors conclude that the presence of 
glycogen in a nutrient solution does not augment the multiplication 
of yeast, as occurs in otherwise suitable media, e. g. dextrose. 
Even small quantities of glycogen do not disappear from a nutrient 
solution exposed to the influence of yeast, though they vanish quickly 
if bacteria contaminate a solution, which no longer shows the glycogen- 
iodine reaction. None of the added glycogen is absorbed by the yeast- 
cells, and not any of the three kinds of yeast were able to make alcohol 
out of it. All the kinds of glycogen employed in the experiments exhi- 
bited the noteworthy property of diminishing both the yeast production 
and the amount of alcohol, not only on suitable (beer-wort) but on 
unsuitable media (meat extract). The three varieties of glycogen used, 
which were prepared from the liver of rabbits and of calves and from 
German yeast, according to Kiilz’s method, behaved exactly alike 
qualitatively, and only exhibited trivial differences in the amount of 
yeast-increase when compared quantitatively. 
* Le Botaniste, iii. (1894) pp. 282-6 (2 figs.). Cf. this Journal, ante, p. 95 
t Cf. this Journal, 1893, p. 509. 
X Centralbl. f. Bakteriol. u. Parasitenk., xvi. (1894) pp. 145-58. 
