4 THE AMERICAN MONTHLY [Jan., 



cells " or " cells of a pastorian form ; " this term does not 

 indicate, however, that they belong to any of the three 

 species of the group Saccharomyces pastorianus. — We 

 further remark that the round cells look more pellucid 

 than the pastorian form does. 



We should now reflect, what this mightbe. The ques- 

 tion of the species is first to be settled, afterwards other 

 questions arise. 



We have before us two forms of cells, but still we 

 might have only one species. We might also have two 

 or more species ; from the form of the cells we can draw 

 no conclusions. It suggests itself that the round cells 

 might belong to one of the cultivated forms Sacch. cere- 

 visiae I Hans., or one of its varieties, and the pastorian 

 cells to one of the wild forms; this cannot be decided 

 but by means of a spore-cultivation. 



II. The spore-cultivation necessitates the keeping of 

 two thermostates, one at 25° C, the other at 15° C. Such 

 thermostates are found in all laboratories, zoological or 

 botanical. It is established that cultivated forms and 

 other forms which generally occur from infection through 

 the air (the so-called wild yeasts) form spores according 

 to the following rules. 



a. Conditions for spore-formation. 



1. Defective nutriment. 



2. Liberal aeration. 



3. Temperature within the limits of optimum to both 

 sides. 



b. Relations of spore-formation to temperature. 

 On this occasion, attention is given only to the general 

 analysis which answers the question Jiow to distinguish 

 hetioeen cultivated and wild forms. This is the most 

 practical point, one most important in practical life 

 where results have to be practically made use of in the 

 brewery. The following table shows how to use the re- 

 sults when the analysis has been made. 



