FERMENTS AND ARTIFICIAL FERMENTATIONS. 79 



all the ferments, and may be regarded as the type of 

 the family. Its cells are round or oval, from eight 

 to nine micro-millimetres in their longest diameter, 

 isolated or united in pairs (Fig. 35). 



When these cells are deposited in a saccharine 

 liquid, which is therefore susceptible to fermentation, 

 vesicular swellings, filled with protoplasm at the 

 expense of the mother cell, may be observed at one 



Fig. 45 Yeast of superior beer Fig 46. Spores of l>eer-yeast, in 



budding (x 4uu diam.). different phases of development. 



or two parts of the surface of the cell ; these swellings 

 increase, acquire the size of the mother cell, and then 

 contract at their base (Fig. 45). They generally arise 

 on the sides of the cell, more rarely on its extremities. 

 The new cells thus formed soon separate from the 

 mother cell, and the protoplasm given up to its off- 

 spring by the latter is replaced by one or two empty 

 spaces, termed vacuoles. When yeast is not in a 

 liquid susceptible to fermentation, it can remain for 

 a longer or shorter time without modification. If 

 abruptly deprived of all nutriment, and especially of 

 sugar, and placed in a sufficiently moist atmc sphere, 



