88 RESEARCHES ON YEASTS. 



cells on the right hand of the figure are from a gelatine cul- 

 ture, and have formed spores ; the remaining cells have been 

 grown under conditions similar to those described in the case 

 of the No. i yeast. The No. 2 yeast is distinguished from the 

 latter by its cells being rounder, and by the presence of giant 

 cells here and there. It gives abundant spore-formation. 



When these two species are examined under the micro- 

 scope with reference to their cell-contents, it is at once seen 

 that the protoplasm of the No. 2 yeast is more uniform and 

 less granular than in the case of the other species, and that 

 the vacuoles are less pronounced. The colonies in wort 

 gelatine given by both species have the ordinary appearance 

 characteristic of the Saccharomycetes. The differences ob- 

 served in the growths of the sedimentary yeasts were also 

 noticeable in the gelatine cultures ; especially the presence of 

 the giant cells mentioned gave a very definite character to 

 the growth of Carlsberg yeast No. 2. In the cases mentioned 

 it was, in short, an easy matter to distinguish the two species 

 from each other by a simple microscopic examination. The 

 figures do not show the differences in form and size as dis- 

 tinctly as they are actually seen, and the different appearance 

 of the cell contents is not represented at all. Jorgensen has 

 described similar observations in his ' Micro-Organisms and 

 Fermentation' (New Edition, London, 1893).* 



* It must not be imagined that the above differences can be regarded as 

 general characters by means of which we are enabled to determine whether a 

 certain species of yeast, of which nothing is known previously, will give a high 

 or low attenuation, will clarify well or badly in short whether in these respects 

 it resembles more closely the one or the other of the two species described, 

 whether it gives a beer of this or that taste, &c. c. To determine this requires 

 much more than a simple microscopic examination. Cultures with giant cells 

 like those of Carlsberg yeast No. 2, are found not only in the case of certain 

 high-fermentation yeasts, but also in species of Tonda (see my figures in ' Compte- 

 rendu des travaux du laboratoire de Carlsberg,' 1883, p. 152) ; and low-fer- 

 mentation yeast cells, the contents of which exhibit a microscopic appearance 

 similar to that of Carlsberg yeast No. 2, may, however, give a strong attenuation 

 and exhibit bad clarifying properties in the brewery. 



Whilst I was chiefly engaged with such investigations I obtained from 

 Mr. Jorgensen's laboratory six low-fermentation yeasts, the properties of which 



