426 SACCHAROMYCES APICULATUS. 



an unfavourable environment, namely, a large vacuole. Nothing 

 has been published hitherto with regard to any further morpho- 

 logical peculiarities of the structure of the cell membrane or 

 contents differentiating the Apiculatus yeasts from the other 

 Saccharomycetes. 



If plate cultures of a mixture of Sacch. apiculatus and Sacch. 

 ellipsoideus be started in must gelatin, the colonies of the former 

 usually make their appearance only after those of Sacch. ellip- 

 soideus have already attained considerable size ; and they remain 

 smaller than the latter throughout. This difference is due, not to 

 any slower rate of reproduction on the part of the first-named 

 yeast, but chiefly to the smaller size of the individual cells, which 

 diminish as the colony increases. The gelatin surrounding the 

 Apiculatus colonies is liquefied at an early stage, and the latter 

 seem also to excrete substances that restrict the further reproduc- 

 tion of the yeast cells. A similar result is observed in the 

 development of streak cultures of Apiculatus yeasts, so that, for 

 the most part, these exhibit merely a delicate, filmy appearance, 

 at a time when the yeast streak in cultures of Sacch. ellipsoideus 

 of the same' age has already grown to a thick white strip. Even 

 after a considerable time the former do not usually show any 

 vigorous development ; and this applies also to the giant colonies, 

 which fail to exhibit any decided, special morphological charac- 

 teristics, and quickly sink in the liquefied gelatin. Farther 

 particulars on this point will be found in the next paragraph. 



310. Racial Differences. 



Sacch. apiculatus, var. paras iticus (see p. 424, vol. ii.), must be 

 considered as a separate variety from the Apiculatus yeast colla- 

 borating in the fermentation of beer and wine, since it differs 

 from these by its strictly parasitic habit, even more than by the 

 shape of the cells. This variety cannot be grown either in fruit 

 juices or in artificial nutrient media. Moreover, the Apiculatus 

 yeasts indigenous on fruit and playing a regular part in vinous 

 fermentation belong to different races and are not of uniform 

 stock, a discovery for which we are indebted to K. AMTHOR (1.) 

 in 1888. Owing to the absence of sporulation and to the great 

 morphological variability of the cells, characteristics of a chemico- 

 physiological nature have to be mainly relied upon in demon- 

 strating the difference, chief among them being the kind and 

 quantity of the metabolic products furnished by cultures of 

 different origin when grown under identical conditions. Thus, 

 Amthor was able to prove the racial divergence of two cultures 

 of Sacch. apiculatus, one of which was isolated from red Heil- 

 bronn must, and the other from a white wine must from Rhenish 

 Hesse. Whereas the former race produced 3.65 per cent, (by 

 weight) of alcohol and 365 mgrms. of glycerin per 100 c.c. of the 



