148 CLASSIFICATION OF THE MICRO-ORGANISMS. 



solid substances with free entrance of air the yeast-lik 

 buds lose their distinctness, the strangulations become 

 less deep, and the whole chain takes on more the form 

 of an elongated hypha-like cell with thicker and thinner 

 places. The cellular chain then represents a mycelial 

 hypha with the apical growth periodically interrupted, 

 but we never find the formation of a complete mycelium 

 consisting of true hyphae, or of typical fruit-bearing 

 hyphae. A marked formation of threads was observed 

 by Grawitz in the cells of mycoderma vini, and the less 

 the amount of sugar present in the nutritive fluid the 

 longer were the threads that were formed ; but constric- 

 tion of the apex or a subsequent segmentation were 

 never noticed, 



Pasteur's Pasteur and Hansen describe under the name of torula a 



group of yeast fungi which do not form ascospores or 

 mycelial threads even on the most various solid substrata, 

 but multiply only by budding as in saccharine fluids. They 

 also occasion very slight or 110 alcoholic fermentation in these 

 fluids, nor do they lead to the formation of a scum on the 

 surface. These torulae, of which Hansen describes five 

 different kinds, are in some places very widely distributed, 

 and can easily be confused with true yeast, because a mor- 

 phological distinction between the two budding forms is not 

 possible. With regard to these torulae it is most probable 

 that they are only development stages of other fungi. 



It has not as yet been possible to distinguish in a 

 satisfactory manner between the different kinds of yeast 

 fungi by morphological and biological character ", 

 because there was no method of cultivation by which we 

 could isolate them, and thus obtain with certainty a 

 pure cultivation of the individual forms. It is only 

 lately that such a separation and classification has been 

 attempted by Hansen and other investigators, but up to 

 the present these attempts Lave not been sufficiently 

 satisfactory to be of use for a handbook. Of the species 

 formerly distinguished from one another, the following 

 may be mentioned here : 



The most im- Sciccharomyces cerevisia (Cryptococcus cer.), the 

 yeast of beer or brandy. Cells spherical or oval, 89 



