18 KANSAS UNIVERSITY SCIENCE BULLETIN. 



conditions, a pair for each of the three media. The^new race 

 persisted in all media, being least prominent in the gelatin. 



Summarizing all experiments with mixed cultures, there is 

 evidence that the new race not only persists in all cultures 

 through as many as sixteen transfers, extending over a 

 period of sixty-five days, but in broth cultures seems to out- 

 grow the parent type. In agar cultures grown at thirty de- 

 grees C, with frequent transfers, the new race diminished, 

 but reasserted itself at once on being transferred to broth, and 

 more gradually by continued transfers on agar at room tem- 

 perature at longer intervals. 



Only one strain of Saccharomyces anomalus, that consisting 

 of the offspring of a single cell isolated from the culture men- 

 tioned at the beginning of this paper, has been employed 

 during the three-year period covered by these experiments ; 

 and during this period the type has varied little as regards 

 its capacity of producing sports. There is no evidence of 

 "mutations periods" arising independently of cultural con- 

 ditions. 



Experiments have been begun to ascertain whether varia- 

 tions similar to those found in Saccharomyces anomalus occur in 

 other yeasts also. A pink yeast isolated from cider was kept 

 under observation for about a month, and many thousands 

 of cells proceeding from a single isolated cell and grown in 

 shallow hanging drops were searched for variations similar 

 to those which originated new races in S. anomalus. Few 

 abnormal cells were found, and these, when isolated, reverted 

 to the parent type. Similar negative results have been ob- 

 tained from a white yeast isolated from cider and from a 

 large-celled white yeast from dough. 



PHYSIOLOGICAL CHARACTERISTICS OF NEW RACES. 



New races of the morphological character described above 

 were tested as to their power of fermenting sugars, their 

 power of liquefying wort gelatin, and their resistance to heat 

 and drying. 



Since the ordinary fermentation tubes do not give reliable 

 quantitative results, a new form of tube was devised. 



This tube (see fig. 1) consists of a glass bulb, a, of 25 or 

 30 cc. capacity, sealed to a U-shaped glass tube, which is 



