46 Discussion 



found in the same situation; if not, I would be concerned about 

 possible special selective features. 



The other point is rather similar, related to the case of sugar fer- 

 mentation — the inconsistency between the results of Hinshelwood and 

 Dean and those of Lederberg and Pollock. I think the cultures that 

 Lederberg and Pollock have been examining should have a complete 

 round trip and return to Hinshelwood' s laboratory and be observed 

 under his conditions again. I would be very pleased, for instance, to see 

 that cultures which they had submitted to some very brief processing 

 would also show large colonies in your media. Sir Cyril, and if they did 

 not, then one could infer that differences in your media have prevented 

 you from seeing this selection in favour of the more rapidly growing or 

 rapidly utilizing mutant. 



