ALCOHOLIC FERMENTS. 141 



film, elongated cells quickly appear, and the growth gradually 

 assumes an appearance perfectly different from that of the 

 sedimentary yeast. 



If we compare the film-formations of the six species, we 

 find that the films developed at the higher temperatures offer 

 very few points of difference which are of use in their exami- 

 nation, Sacch. cerevisice I. and Sacch. ellipsoideus II. being 

 alone distinguishable from the remainder. It is quite other- 

 wise, 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 cul- 

 tures 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 likewise found between the otherwise similar species Sacch. 

 ellipsoideus I. and //. 



An examination of the limits of temperature for the 

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

 Sacch. ellipsoideus I., these lie within about 38 and 5 to 

 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 mentioned species, whilst its maximum tempera- 

 ture, however, 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 the 

 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 the 

 flasks with this yeast can be recognised by this alone. 

 Thus, at 22 to 23 C. the film 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 



