MODERN RESEARCHES INTO THE NATURE OF YEAST. 153 
must usually be referred to Chalara, although not with 
certainty, as the cells of Oidium lactis and of Mycoderma vary 
widely in diameter. 
It is not very often that all three fungi are produced to- 
gether; the Chalara being the one most frequently wanting. 
They are probably all derived from the solid substance used for 
making the infusion, where they either occur as such, or are 
developed from conidia, mycelial cells, or ascospores, when 
water is poured on to it. When the fluid is very clear, as in 
the case of wine, the first traces of pellicle consist entirely of 
Mycoderma cells, followed invariably by Oidium lactis. 'The 
three forms appear to maintain their constancy under all 
conditions. In fluids in which alcoholic fermentation has 
taken place, Cienkowski found all three. There can be little 
doubt that the various species described by Reess under the 
names of Saccharomyces apiculatus, pastorianus, &c., are all 
forms of Mycoderma vini. Whether the cycle of development 
of Saccharomyces is as limited as Reess supposes, or whether 
it may ultimately be found to include Oidiwm lactis and 
Chalara, may still be considered an open question. It must 
be left also for future researches to determine how far the 
cycle of development of Saccharomyces (Torula) cerevisie 
corresponds to that of Mycoderma vini. 
The resemblance between the mycelia of the different 
yeast-fungi is so great as to justify the hypothesis of their 
identity. It must, however, be admitted that at present we 
do not know of a single fact which places beyond doubt this 
extremely probable hypothesis. Very early in his researches 
Cienkowski apparently found Chalara-mycelia which had 
put out Mycoderma-buds from their branches as well as 
from the closely connected cells, and at the time considered 
this fact to establish conclusively the genetic connection of 
the two fungi. He had not, however, then learnt the 
difficulty of distinguishing between the two, and was subse- 
quently led to believe that the filament represented a conidial 
form of Mycoderma. 
There are also phenomena which appear to point to a 
connection between Chalara and Oidium. If both organisms 
are allowed to grow in damp air under cover-glasses, and 
only a very small amount of fluid supplied, it is sometimes 
observed that an Otdiwm-hypha suddenly developes into a very 
long slender filament, bearing a small spherical cell at the 
extremity, like Chalara. The thick part of the hypha 
then breaks up into the usual chain of conidia, which 
remains completely connected with the extremely elongated 
terminal cell. ‘Ihe mode of formation of the small spherical 
