110 BACTERIA. 



the room it goes on very slowly, taking a whole month to 

 form a comparatively delicate membrane. In very old 

 cultures well-marked mycelium formation may be met with 

 in which the cells are ellipsoidal, elongated, or sausage- 

 shaped, or somewhat club-shaped. It is capable of acting 

 on grape sugar ; it inverts cane sugar and ferments it ; but 

 has no action on maltose, lactose, or dextrine in yeast water, 

 nor does it attack starch. 



8. Saccharomyces Marxianus, named after its describer, 

 was first found in wine. Hansen studied it most closely. 

 He found that in beer it develops as small ellipsoidal 

 and egg-shaped cells, with here and there sausage-shaped 

 cells, which are often combined into colonies. There 

 are developed on a quiescent fluid small viscid masses, some 

 of which remain on the surface whilst others sink to the 

 bottom. The film develops exceedingly slowly, but in it 

 are found cells which resemble very closely those of the films 

 of the first six species of Saccharomyces described. The 

 true film contains oval and short sausage-shaped cells. 

 The spores are not freely developed. When it is grown on 

 solid nutrient media spores are more frequently formed, in 

 which case they are usually oval or kidney-shaped. In beer 

 wort this yeast is not very active, nor is it able to ferment mal- 

 tose, but it acts vigorously on saccharose, inverting it and then 

 fermenting it with great activity ; it also acts upon dextrose. 



9. Saccharomyces exiguus, found by Hansen in German 

 yeast, differs from the preceding Saccharomyces in the fact 

 that it forms no mycelial threads on beer wort, or on solid 

 nutrient media. It forms spores, but sparsely, and the film 

 is exceedingly delicate, the cells of which this is made up 

 being short rod-shaped or ovoid. It acts on the sugars exactly 

 as does the Saccharomyces Marxianus. 



10. A somewhat peculiar Saccharomyces belonging to this 

 group is the Saccharomyces membrancefaciens, which forms 

 on beer wort a bright yellow tough scum, composed of long 

 and sausage-like cells, which may be closely packed together 

 or may occur singly. It forms spores rapidly, liquefies nutrient 

 gelatine, and is peculiar from the fact that it does not cause 

 fermentation of any of the ordinary carbo-hydrates, nor has 

 it any effect in inverting cane sugar. 



n. Saccharomyces minor (Engel), who describes it as 

 spherical cells 6/* in diameter, arranged in chains of 6-9 



