INULASE FORMATION IN ASPERGILLUS 83 



greatly increased, and that the amount present is greater in cul- 

 tures two days old than in those that are three days old. The 

 results obtained with Pencillium glaucum and P. hijorme are 

 essentially the same as for Aspergillus niger. Glucose is without 

 influence on the formation of invertase but its presence makes the 

 inversion of the sucrose of the culture medium somewhat slower. 

 It is suggested that this may be a case of chemical balance, 

 glucose being one of the end products of the hydrolysis of 

 sucrose. 



Kylin finds that the inversion of maltose in the culture medium 

 is similarly hindered by the presence of glucose in it. Maltase 

 is formed not only when maltose is the source of carbon but also 

 when glucose, sucrose, quinic acid or starch are substituted for 

 maltose. The formation of maltase in the presence of maltose 

 is greatly increased but larger amounts of maltose do not result 

 in a corresponding increase in the amount of tlie enzyme produced. 

 The presence of glucose ti;gether with maltose does not cause a 

 decrease in maltase formation. The results of the studies on the 

 two species of Penicillium are similar to the results obtained with 

 Aspergillus. 



Kylin finally concludes that his results give evidence of quan- 

 titative enzyme regulation only and no evidence whatever of a 

 qualitative regulation. The results of all workers, who have 

 found a qualitative enzyme regulation with the exception of 

 the work of Knudson on tannase, are questioned by Kylin. 



C. METHODS AND MATERIALS 



The correlation of the experiments here presented with those 

 of previous investigators along similar lines made it desirable 

 that a single well known organism, which had been rather thor- 

 oughly investigated along other physiological lines, be selected as 

 the main object of study. For this reason and for the reason 

 that it grows well on liquid media, Aspergillus niger was selected. 

 This species is readily identified and easily maintained in pure 

 culture, giving it an additional advantage over the use of many 

 other forms. Stock cultures were maintained on ordinary potato- 



