682 THE AMERICAN NATURALIST. [VOL XXXII. 
whose characteristic function is to invert and ferment the 
different sugars. Here we have a group much more limited in 
number of species than the bacteria, but like them microscopic 
and rapidly growing. Although not long ago they were classi- 
fied after a fashion on their morphological characters, the 
admirable investigations of E. C. Hansen and his followers have 
pointed out the important fact that these characters, taken by 
themselves, are less fixed, although the limits of their variation 
may be fixed, than certain physiological characters such as the 
maximum and minimum temperatures of growth, and especially 
the temperature at which spore formation takes place. It is in 
these last-named characters, rather than in the former, that the 
specific distinctions in Saccharomycetes are sought by those 
who study that group specially. 
The same objection is urged by botanists in this as in the 
case of bacteria, that the so-called species are not species, but 
races. We naturally ask, races of what species? There have 
been many attempts to determine the origin of the common 
Saccharomycetes, and the question has been supposed more 
than once to be settled. Without intending to imply that the 
question is not still open to investigation, I must admit that 
there does not yet seem to me to be any satisfactory proof to 
show from what higher forms Saccharomycetes have been 
derived. Although there can be no doubt that in the germina- 
tion of spores of certain fungi, especially the Ustilaginacee, 
bodies are produced in abundance which not only closely 
resemble Saccharomycetes in shape, but also, in some cases 
at least, are capable of producing alcoholic fermentation to a 
limited extent, it does not seem to me that that is by any means 
enough to warrant the opinion expressed by Brefeld that the 
Saccharomycetes are derived from, and are degenerate con- 
ditions of, Ustilaginacez. In fact, one has only to consult 
Brefeld’s own writings to see that Saccharomycetes-like bodies 
are produced by the germinating spores of other orders of fungi 
than Ustilaginacez, and it is known that, in some species, as in 
the genus Aspergillus and in certain Mucoracez, the budding 
cells which look like the Saccharomycetes, oes the sou in oi 
limited sense, are also capable of producing alcol oe 
