BIOGRAPHICAL MEMORANDA 



was cultivated in a galactose-free medium, and thereafter exposed to 

 this sugar. The appearance of the ability to ferment galactose was 

 determined, and an attempt was made to relate this to growth as 

 determined by cell counts. The results of these experiments were, 

 however, inconclusive; and it was not until 1936 that the careful 

 studies of Stephenson and Yudkin [1936] convincingly showed that 

 the adaptation to galactose can take place in the absence of cell multi- 

 plication. 



Scientifically the most interesting part of the thesis is that which 

 deals with the studies on fermentation and assimilation of certain 

 sugars by yeasts. It casts a clear light on Kluyver's unusual ability to 

 perceive the difficulties that may arise out of an uncritical acceptance 

 of experimental results that would appear to be at variance with well- 

 established and rational ideas ; to detect potential flaws in experimental 

 procedures; to devise experiments for decisively testing the merits of 

 alternative hypotheses; and to synthesize conflicting interpretations. 



In 19 10 Rose had discovered that Endomyces magnusii, a yeast that 

 readily ferments glucose, fails to grow in Hayduck's medium* with 

 this sugar as the principal carbon source, yet develops profusely if 

 maltose, which is not fermented by this species, is substituted for the 

 glucose. Shortly afterwards Lindner and Saito, as well as Kita, had 

 found that a number of other yeast species behave similarly. From 

 these results the conclusion had been drawn that glucose cannot, 

 whereas maltose can be assimilated by such yeasts. 



This situation was anomalous enough to warrant a more detailed 

 investigation. The above-mentioned observations seemed to violate 

 some fundamental ideas on the degradation of oligosaccharides via 

 the constituent hexose units, and on the significance of fermentation 

 as the ultimate energy source for yeast during anaerobic existence. 

 Evidently Kluyver was reluctant to abandon these concepts, for 

 which a considerable body of sound experimental evidence had been 

 amassed in the course of time, and hoped that it might be possible to 

 find a more satisfactory explanation for the aberrant results. 



First of all he repeated and readily confirmed the previous experi- 

 ments of Rose, Lindner and Saito, and Kita. He also found several 

 yeasts among his own collection that exhibited essentially the same 



* Tapwater, 0.025 P er cent MgS0 4 , 0.5 per cent KH 2 P0 4 , 0.5 per cent asparagine, 

 5 per cent sugar. 



76 



