264 HEREDITY IN SACCHAROMYCETES. 



produced constantly asporogenic cells, which was, however, not 

 the case when the culture was left undisturbed. Here, again, 

 the high temperature shows itself the modifying factor. 



The oldest asporogenic varieties obtained from the different 

 species have now been in existence for more than sixteen years, 

 and have remained constantly asporogenic although repeatedly 

 cultivated under highly divergent conditions. 



It is found to be the rule that loss of sporogenic power is 

 accompanied by loss of the capacity for producing film growths. 

 In some species the variety has been found to possess a greater 

 reproductive capacity than the original form, and possibly this 

 applies to all. The asporogenic varieties also exhibit considerable 

 fluctuations in respect of the production of alcohol. Since, as 

 mentioned on p. 126, vol. ii., the film cells of Saccharomycetes are 

 able to decompose alcohol into carbon dioxide and water, a power 

 not shared by the sedimental yeast cells (at least so long as the 

 liquid is of sufficient depth), the quantity of alcohol formed in 

 wort fermented by an asporogenic (and therefore filmless) variety 

 does not become appreciably less when left to stand in a flask (e.g., 

 Pasteur flask) precluding evaporation. 



In addition to the instance of an accidentally produced constant 

 variation observed with Saccharomy codes Ludwigii (p. 260, vol. ii.), 

 mention may be made of LEPESCHKIN'S (I.) observation of the for- 

 mation of mycelium by Schizosaccharomyces Pombe and ScMz. 

 mellacei. No particulars are given by this worker respecting the 

 conditions under which this result was obtained, but he states that 

 the phenomenon remained constant during numerous generations 

 and that it was found impossible to secure reversion to the 

 original form of single cells. 



275. Hansen's Experiments with Top and 

 Bottom Yeast. 



Special interest attaches to HANSEN'S (XLV.) latest researches 

 into variations in fermentative habit, namely, the appearance of top- 

 fermentation yeast cells in a typical bottom yeast, and vice versd. As 

 mentioned on p. 260, vol. ii., he had previously observed the faculty 

 of certain bottom yeasts for temporarily producing top-fermentation 

 phenomena after storage at a low temperature. In this connec- 

 tion he instituted some very comprehensive researches with Sacch. 

 turbidans ( = Sacch. ellips. //.), a trace of a vigorous young vegeta- 

 tion being transferred to Freudenreich flasks charged with a thin 

 stratum of wort and kept at 0.5 0. At the end of three and five 

 months the cultures were examined, by sowing an average sample 

 in wort contained in test -glasses. In every instance the fermen- 

 tation phenomena were decidedly those of top fermentation, so 

 that all or most of the cells had acquired a top-fermentation 

 habit. Test-glasses were used because of the necessity for 



