I20 BACTERIA 



of the cell a slight swelling or protuberance appears, which 

 slowly enlarges. Ultimately there is a constriction, and the 

 bud becomes partly and at last completely separated from 

 the parent cell. In many cases the capsules of the daugh- 

 ter cell and the parent cell adhere, thus forming a chain of 

 budding cells. The character of the cell and its method of 

 reproduction do not depend merely upon the particular 

 species alone, but are also dependent upon external circum- 

 stances. There are differences in the behaviour of species 

 towards different media at various temperatures, towards the 



AscospoRE Formation 



carbohydrates (especially maltose), and in the chemical 

 changes which they bring about in nutrient liquids. In 

 connection with this Professor Hansen has pointed out that, 

 whilst some species can be made use of in fermentation 

 industries, others cannot, and some even produce diseases 

 in beer.' 



One of the most remarkable evidences of the adaptability 

 of the yeasts to their surroundings and a specific character- 

 istic occurs in what is sometimes called ascospore formation. 

 If a yeast cell finds itself lacking nourishment or in an un- 

 favourable medium, it reproduces itself not by budding, but 

 by forming spores out of its own intrinsic substance, and 

 within its own capsule. To obtain this kind of spore form- 

 ation Hansen used some gypsum blocks as medium on which 



^ E. C. Hansen, Studies in Fermentation (Copenhagen), p. 98. 



