244 MICRO-ORGANISMS AND FERMENTATION. 



done by HANSEN, until systematic classification has been further 

 developed. 



, This ferment was the subject of one of the finest and most 

 thorough biological investigations of our time, for HANSEN was 

 enabled, after several years' work, to determine both its habitat 

 in nature and its regular migrations at the different seasons of 

 the year. The reason why this species was selected for the 

 investigation was that, while other species occur in very varied 

 and uncertain forms, making the study of their occurrence in 

 different localities very difficult, this ferment can be recognised 

 with certainty, for it always occurs in cultures with lemon- 

 shaped cells ; this is the typical form of the species. 



Sacch. apiculatus occurs abundantly in wine-yeast, especially 

 during the first stages of the fermentation, also in spon- 

 taneously-fermented Belgian beer ; in nature it is found 

 abundantly on ripe, sweat, succulent fruits. 



If a little of such a growth is examined under the micro- 

 scope in a drop of nutritive liquid, the development of the 

 fungus can be followed. This is very characteristic (compare 

 Fig. 78). It is seen that the buds formed from the typical 

 lemon-shaped cells may be either lemon-shaped (a, &, c, e, f) or 

 oval (a c) ; it is also noticed that the oval cells must first 

 form one or more buds before they are able to assume the 

 lemon-shape (e -/), and finally, that the lemon-shape of a 

 cell attained by budding (k, ~k' } k") may be lost again on the 

 formation of a new bud (&'"). Under other conditions the cells 

 may assume quite different forms, sausage-shaped, half-moon- 

 shaped, bacteria-like, etc. (g m). Now, does any rule govern 

 this apparent confusion of forms ? It has just been shown 

 that the fungus can form two kinds of buds, and that the oval 

 buds must develop one or more new buds before they can 

 assume the typical form. The question then is : Under what 

 conditions are those two kinds of buds developed ? It was 

 shown by means of culture experiments that the lemon-shaped 

 buds are developed especially during the first stages of the 

 culture, but are afterwards crowded out by the oval forms. 



We shall now give a further description of the fungus from 

 a physiological and biological standpoint. 



Saccharomyces apiculatus is a bottom-fermentation yeast > 



