142 A. W. BENNETT, 
Some Account of MoprerN ReEsEARCHES into the NATURE 
of Yeast. By A. W. Bennert, M.A., B.Sc., F.LS., 
Lecturer on Botany at St. Thomas’s Hospital. 
Tue long-received hypothesis that yeast is genetically 
connected with various species of mould has been subjected 
to severe criticism by de Bary,! and still more recently by 
Reess,? who have clearly shown that we have at present no 
sufficient reason for assuming a genetic connection between 
the two groups of organisms. Since his discovery of the 
occurrence of ascospores in beer-yeast, Reess has, on the con- 
trary, endeavoured to establish the claim of ferment-fungi to 
be considered as organisms sui generis allied to Endomyces 
and Taphrina (Exoascus). 
Reess set himself to investigate the problem whether the 
vegetative form of Saccharomyces which occurs in fluids sus- 
ceptible of alcoholic fermentation embraced its whole course 
of development, or whether when removed from these media 
it would exhibit other phenomena of growth and especially 
of reproduction. 
The usual materials for the culture of fungi—fresh or 
preserved fruit—were unsuitable in this case on account of 
their natural richness in sugar. But slices, both raw and 
cooked, of potato, Kohl-rabi, Jerusalem artichoke—and, not- 
withstanding its containing sugar, of carrot, proved suitable. 
On the surfaces of these slices the pulpy yeast which has 
settled —bottom-yeast—was spread in a layer as thin as pos- 
sible. The superfluous water was then allowed to evaporate 
under a bell glass. The culture must be conducted in an 
atmosphere so regulated that it is always moderately moist. 
Drops of water must not be allowed upon the cultures, since 
with over abundant moisture the ordinary form of yeast will 
be reproduced, or other organisms will make their appearance, 
and clear the field. Bacteria will speedily get the upper 
hand and even infusoria, which will consume the yeast-cells. 
For the first two or three days the yeast presents much the 
same appearance as in a fermentible fluid of weak concentra- 
tion. The cells, which contain much water and large 
vacuoles, bud. In twenty-four hours the edge of the 
layer of yeast advances in wavy projections 3—{ mm. The 
cells themselves are roundish, seldom elliptic or spindle- 
shaped. No outgrowth of the yeast-cells into mycelial fila- 
1 De Bary, ‘Morphologie der Pilze,’ 1861, p. 181. 
* Reess, ‘ Botanische Untersuchungen tiber die Aleoho!gahrungspilze,’ 
1870. 
