ALCOHOLIC FERMENTS. 



161 



the case of the three species of the group Sacch. Pastorianus. 

 A relationship is thus shown to exist between the influence 

 of temperature on budding and fermentation on the one hand, 

 and film-formation on the other. 



In brewers' low-fermentation yeasts, and in some wild 

 yeasts, WILL observed round and oval cells, having a thick 

 membrane and containing a number of small oil-drops (Fig. 44) 



FIG. 44. Durative cells (after WILL). The outer layer of the membrane is partly 

 or completely detached, a, 6, in wort ; c-f, in mineral nutrient solution. 



These occurred in the rings of yeast and in the small surface 

 patches preceding true film-formation. If treated with concen- 

 trated hydrochloric acid, the membrane splits into two layers. 

 In cultures, especially in artificial nutrient liquids, the outer 

 layer of this membrane gradually detaches itself; sometimes in 

 such a way that the outer layer is not torn, so that it appears 

 as if the cell contained another cell. The cell contents are 

 coloured green or brown by concentrated sulphuric acid. The 

 glycogen reaction with iodine has been occasionally observed 



