IO8 BACTERIA. 



tion process as does the Saccharomyces cerevisiae on the 

 various carbo-hydrates on which that ferment acts. 



3. Saccharomyces ellipsoideus II. is also a " wild " or wine 

 fermentation yeast which gives rise to the muddiness of beer. 



It is essentially a low yeast, the film that forms is exceedingly 

 delicate ; it makes its appearance in from three to four days at a tempera- 

 ture of 33 to 34 C., but not for five or six months at 3 to 5 C. At 

 2 and at 40 C. no film forms. Young cultivations at 15 C. are 

 usually somewhat rounded or egg-shaped, whilst the older cultures show 

 longer mycelial rods, with forked transverse shoots given off at the joints. 

 Asci containing from two to four spores may be egg-shaped, slightly 

 irregular or elongated. The spores measure from 2 to 5/i in diameter ; 

 they are developed most rapidly at 29 C., most slowly at 8 C., and are 

 not formed at above 35 or below 4 C. 



Hansen does not look upon Saccharomyces Pastor ianus as 

 a pure species ; he divides it into three. 



4. The first of these, Sacch. Pastorianus I. (Hansen), is a 

 wild yeast, spores of which frequently occur in the atmosphere 

 of breweries. It gives an unpleasant bitter taste to beer ; it, 

 also, is a bottom ferment, occurring as elongated ellipsoidal 

 or pear-shaped cells, from which small apical or lateral 

 branches may be given off. 



The asci are usually elongated or rounded ; they may contain two 

 spores or multiples of two, up to eight or even more. The spores vary 

 very much in size from 1.5 up to 5/i ; are developed most readily 

 (twenty-four hours) at a temperature of 27.5 C. ; most slowly (fourteen 

 days) at a temperature of 3 to 4 C. The spore formation ceases at .5 C, 

 and at 3 r '5 C- The films are usually very delicate, are developed most 

 readily (seven to ten days) at from 26 to 28 C., most slowly (five to six 

 months) at from 3 to 5 C. , development ceases altogether at 34 and 2 C. 

 At from 3 C. to 15 C. mycelial-like threads are developed pretty freely in 

 this film and most irregular forms make their appearance ; many irregular 

 club and skittle-shaped and other forms are formed in the older films, but 

 fewer in the younger ones ; in these films the cells are usually smaller. 



5. Saccharomyces Pastorianus II. (Hansen) was also 

 separated from the air of the brewery. In gelatine made 

 with yeast water it grows along the line of the inoculation 

 streak (at 15 C. at the end of sixteen days) in the form of 

 colonies with smooth edges. It is a feeble top fermentation 

 yeast when grown in beer wort. 



The sedimentary cells of this yeast are mostly elongated, but they may 

 be slightly rounded, varying considerably in size. The cells found in the film 

 are rounded, egg-shaped, or somewhat elongated. The spores are from 2 

 to 5 a in diameter ; the asci are usually elongated and the spores occur in 

 multiples of two. They are formed most rapidly (twenty-seven hours) 



