THE PATHOGENIC FUNGI AND YEASTS 439 



those of the same species or the same culture. In old colonies indi- 

 viduals may be found hardly larger than cocci, 1 to 2/t, while in other 

 colonies, especially on the surface of a liquefied medium, giant yeast 

 cells are found often attaining a diameter of 40// or more. In spite of 

 these wide fluctuations, however, the various species are characterized 

 by a fairly definite average in size and form. 



During the process of budding the nucleus of the cell moves toward 

 the margin, where it divides. At this point the limiting membrane of 

 the cell ruptures or a hernia-like protrusion develops which has the 

 appearance of a button attached to the cell. The daughter-cell so 

 formed rapidly increases in size and gradually assumes the shape and 

 size of the mother-cell. 



A fact of the utmost importance for the propagation of the blasto- 

 mycetes and continuation of the species is the formation of spores. In 

 this also the cell nucleus takes part, dividing into several fragments, 



FIG. 139 



.--* 



. 



- 



f 



< 



"-* ' 



Saccharomyces Busse. X 350 diameters. (From Kolle and Wassermann.) 



each of which becomes tlie centre of a new cell lying within the original 

 cell. These new cells possess a firm membrane, a cell nucleus, and a 

 little dry protoplasm. The number of spores developed in the yeast cells 

 varies, but is constant for a given species. As a rule, one cell does not 

 produce more than four endogenous spores, so-called astrospores; but 

 species have been observed e. g., schizosaccharomyces octosporas (Beijer- 

 inck) in which eight spores are found. 



The vitality of yeasts is truly enormous. Hansen as well as Lindner 

 were able to* obtain a growth from cultures twelve years old. Busse 

 succeeded in getting a luxuriant growth from a dry potato culture 

 seven and a half years old, and almost as hard as bone. 



As stated above, the most important property of yeasts is that of 

 producing alcoholic fermentation. While a large number of yeasts are 

 merely able to decompose dextrose into alcohol and carbon dioxide, 

 there* are some which ferment cane-sugar, others which invert and 

 ferment starch; in fact, all kinds of carbohydrates may be decomposed. 



