SACCHAROMYCETES. 253 



.S". Cerevisics I. to thirty-six hours in 6". Pastoriafius II. The dia- 

 gram which accompanies this article embodies these results in a 

 way which admits of ready comparison, the differences between 

 the species being so marked when the cultures are made at a 

 temperature of 52° F. as to indicate pretty correctly to which 

 species each belongs. The experiments recorded in this diagram 

 were made with a laboratory yeast, which, no doubt, had a Conti- 

 nental origin, and the figures thus obtained do not hold good for 

 English " high-fermentation '"' yeasts, which have been cultivated 

 under very different conditions of temperature and nutriment to 

 those employed above. 



The details of the experiments by which the results shown on 

 the diagram were obtained will be of interest to the reader. Fully- 

 developed but somewhat inert cells, of a pure culture in each case, 

 were transferred to suitable flasks of sterilised malt infusion, and 

 allowed to develop for twenty-four hours, when the liquid was 

 carefully poured off and a fresh supply of the same malt infusion 

 introduced. This is necessary in order to obtain thoroughly 

 vigorous cells, from which alone spores are likely to be formed. 

 At the end of another twenty-four hours — (the time must be 

 observed precisely) — the deposited yeast was removed by means 

 of sterilised platinum foil or wire to gypsum and gelatin tablets (of 

 course, steriHsed), which were placed in suitable appliances for 

 maintaining constant temperatures. A careful and frequent 

 microscopic examination was then kept up in order to detect the 

 earliest traces of spore formation, the time of the first indication 

 of such change being carefully recorded against the temperature at 

 which the culture had been maintained. Similar observations were 

 simultaneously made on a series of cultures from the same yeast, 

 carried on at various temperatures, and the results showed, as was 

 expected, a regularly-varying period of spore development for 

 each variation of heat, which, being properly registered, may be 

 made the basis for a chart somewhat similar to that employed in 

 recording changes of temperature in the human subject. The 

 chart attached to this article contains the curves for the three 

 species named, which have been the subject of special experiment. 



It will be readily understood how the data which can thus 

 be obtained without much difficulty in a physical laboratory, 



