FERMENTATION. I07 



in diameter. Film formation takes place most rapidly (seven to ten days) 

 at a temperature of from 20° to 22°, most slowly (two to three months) at 

 6° to 7° C, and ceases altogether at 38° C, and at 5° C, at the other extreme. 

 Between 20° and 30° C, the cells are frequently sausage-like and irregular ; 

 from 6° to 15° C. the cells are usually like the parent cells in younger 

 cultivations, but in older cultivations the forms are like those already 

 described. 



This species, like all those investigated by Hansen, secretes 

 a peculiar substance, which, acting on saccharose or crude 

 cane sugar, inverts it to " invert " sugar ; the yeast then brings 

 about the fermentation of this latter substance, and also of 

 dextrose and maltose, giving rise to the formation of alcohol 

 and carbonic acid gas, with an evolution of heat and great 

 multiplication of the yeast-cells. It does not seem to exert 

 any action on lactose or milk sugar. In this respect these 

 ferments resemble mucor racemosus, which first brings about 

 the inversion of cane-sugar ; it also secretes invertase, which 

 causes inversion of saccharose, the products of which it 

 ferments ; it also sets up a weak fermentation in beer wort 

 of the maltose and dextrose present in that liquor. 



Reess' genus of Saccharomyces ellipsoideus Hansen divides 

 into two — I. and II. 



2. Saccharomyces elltpsoideus I. is really a '' wild " species 

 of wine ferment ; in beer wort it grows as a low yeast. It is 

 usually rounded or eUipsoidal in shape, though it sometimes 

 assumes the sausage form. The spores, of which two to four 

 are usually found in a single ascus, are from 2 to 4/1 in 

 diameter. 



These spores develop most rapidly (in twenty-one hours) at 25° C, most 

 slowly (eleven days) at 7.5° C, and are not formed at all at 32. 5° C. at the 

 one extreme, and at 4° C. at the other. Grown on the surface of beer wort 

 gelatine, its colonies form a peculiar net-work along the line of the inocula- 

 tion streak. The surface membrane is formed rapidly (eight to twelve 

 days) at a temperature of from 33° to 34° C, most slowly (sixty to ninety 

 days) at 6° to 7° C. ; it is always a delicate membrane, and cannot be grown 

 at S° C. on the one hand and at 38° C. on the other. 



The most characteristic growth takes place at from 13° to 

 15° C, when it occurs as a complicated branching mass, 

 with elongated cells, or threads, arranged in rows, with 

 several lateral processes coming off at the points of junction. 

 Secondary branches are formed at the constrictions of the 

 primary branches. 



It appears to exert as powerful and rapid a fermenta- 



