160 MICKO-ORGANISMS AND FERMENTATION. 



otherwise, however, when young films developed at a temperature 

 of 13 to 15 C. are examined. The two species, Sacch. 

 Pastorianus II. and Sacch. Pastorianus III. which are both 

 top- fermentation yeasts, and which in the ordinary cultures 

 cannot be distinguished from each other with certainty by 

 the form of their cells exhibit in this case entirely different 

 forms of growth ; and an equally striking difference is found 

 between the otherwise similar species Saccli. ellipsoideus I. 

 and II. 



An examination of the limits of temperature for the forma- 

 tion of films shows that for Sacch. cerevisice I. and Sacch. 

 ellipsoideus /., these lie approximately within 38 and 5 6 

 C. ; the limits for the three Pastorianus species are 34 and 

 3 C. ; Sacch. ellipsoideus II. has the same lower limit as the 

 last species, but its maximum temperature is 38 to 40 C. 



The time limits, when compared with those previously given 

 for ascospore-formation, show that in both cases the development 

 takes place more slowly at low than at higher temperatures ; at 

 temperatures near to the minimum and maximum limits only 

 a very slight and imperfect film-formation is ever obtained. 



At temperatures above 13 C. the film of Sacch. ellip- 

 soideus II. develops so rapidly and vigorously that flasks 

 containing this yeast can be recognised by this alone. Thus, 

 at 22 to 23 C. the film had completely covered the surface 

 at the end of six to twelve days, whilst in the case of the 

 other five species a period three times as long was required 

 for the formation of films, and these were generally more 

 feebly developed. This species and Sacch. Pastorianus III. 

 also develop a vigorous film with comparative rapidity at the 

 ordinary room temperature, the other species being left far 

 behind. 



We have said that the film-formations have different 

 maximum temperatures. This is related to the fact that the 

 maximum temperature for budding is not the same for the 

 different species. It was proved that budding and fermentation 

 can take place at temperatures at which film-formation no longer 

 occurs. Thus, in the case of Sacch. cerevisice /., Sacch. ellipsoideus 

 I. and Sacch. ellipsoideus II., HANSEN still observed a vigorous 

 fermentation and budding at 38 to 40 C., and at 34 C. in 



