96 RESEARCHES ON YEASTS. 



both have sprung from a single cell.* When some flasks 

 containing wort are inoculated from these colonies, so that 

 each of one series only receives cells from a colony containing 

 the Pastorianas form, and each of a second series only cells 

 from a colony with the cerevisicz form, it will be found that 

 the growths obtained in the wort will exhibit the same 

 difference; if, however, the cultivation is continued further, 

 the difference between the two series will become less, the 

 sausage-shaped cells gradually disappearing, so that finally 

 all the growths will consist of oval cells. In one experiment, 

 however, it was only after seven such cultivations that the 

 oval cells predominated, the original culture consisting of 

 sausage-shaped cells. The time during which this occurred 

 was about two months. In these experiments, each new 

 growth was obtained by inoculating with a very small sample 

 of the sedimentary yeast from the preceding culture, pre- 

 cautions being, of course, taken to prevent the pure cultures 

 from becoming contaminated. Whilst the sausage-shaped 

 cells still preponderated, I introduced some of the yeast 

 into the propagating apparatus in the fermenting cellar of 

 Old Carlsberg. Even after ten days, the growth which had 

 formed consisted mainly of oval cells, and when this was 

 used as pitching yeast in a larger vessel, a typical yeast 

 consisting of oval cells was at once obtained. The oval 

 form was tested in a similar manner on the large scale, and 

 here again it retained its oval form. Both gave beers of the 

 same character, and were thus proved also to belong to the 

 same species. 



These experiments teach us that there is a difference in 

 the indwelling properties of the individual cells, and therefore 

 a microscopic examination of the yeast colonies in wort gela- 

 tine gives us as little information about the species in question 



* I have in previous communications also pointed out that colonies in wort 

 gelatine grown from the same species of Saccharomyces may yet present a 

 different appearance when examined with the naked eye or with a low power. 



