92 UNIVERSITY OF WISCONSIN STUDIES 



nearly identical characters. The other two included only a 

 few cultures and were of doubtful validity. 



The value of divisions based on the liquefaction of gelatin 

 may be very properly questioned. It is well known that the 

 ability to excrete a proteolytie enzym may be lost and Burton 

 and Rettger think that there may be an error in determina- 

 tions which do not permit an incubation period longer than 

 20 days. If the fact of gelatin liquefaction can be established, 

 there is no doubt that it indicates a distinct evolution in 

 methods of obtaining food supply and consequently has tax- 

 onomic significance. The indications are that the liquefiers 

 of our high ratio group have other characters in common 

 which separate them from the non-liquefiers arid we have ac- 

 cordingly considered them separately. 



Gelatin- c*. = /.$ - 3,0 V.andt?* 



Fig. 4 



While there is a considerable range in the gas ratio of the 

 high ratio group, the variation under different conditions and 

 between cultures otherwise identical is so great that this 

 character cannot be safely used for further subdivision. Many 

 groupings on the basis of substances fermented are possible. 

 The correlation of adonitol fermentation with a definite source 

 has suggested the use of this character as a possible indicator 

 of a line of demarcation. 



The differences in the two groups formed in this way are 

 shown by Fig. 4, which is based on data given in Table IV. 

 The adonite -f- cultures are more active in every way than 

 the adonite cultures, and are especially so in fermenting 



