ALCOHOLIC FERMENTS. 159 



temperatures, and occurs most markedly with those species 

 which give rise to the most vigorous film-formation. 



The preliminary cultivation of the cells is the same as that 

 previously described (spore-formation). The liquid is then 

 decanted from the growth obtained, and fresh sterilised wort is 

 added ; the mixture of yeast and wort is agitated, a drop 

 is transferred with the usual precautions to an ordinary 

 flask of about 150 c.crn. capacity, half filled with wort, and a 

 piece of filter-paper is then tied over its mouth. HANSEN 

 exposed flasks treated in this way to different temperatures, 

 and determined : 



1. The limits of temperature for the formation of films; 



2. The approximate length of time required for their 

 formation at different temperatures ; and 



3. The microscopic appearance of the growths at different 

 temperatures. 



The main point in these investigations of the six species 

 previously mentioned is to determine the microscopic appearance 

 of the films of these species, formed at the same temperature ; and 

 here again, if we may regard the results from a different point 

 of view to that adopted in the last section, we have a complete 

 investigation of the relation between the influential factors and 

 the forms produced, demonstrating that we are dealing with so 

 many perfectly distinct types or species. 



The examination of the films was made, unless otherwise 

 stated, when they had so far developed that they were just 

 visible to the naked eye. 



A glance at the illustrations representing these film-growths 

 (see description of the species) will show that their general 

 character is different from that of the sedimentary forms. For 

 instance, the sedimentary form of Sacch. cerevisicv I. is oval or 

 spherical, whilst in the film, elongated cells quickly appeal 1 , 

 and the growth gradually assumes an appearance perfectly 

 distinct 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 would be of value in their 

 examination ; Sacch. cerevisice I. and Sacch. ellipsoideus II. 

 being alone distinguishable from the remainder. It is quite 



