328 THE BACTERIOPHAGE AND ITS BEHAVIOR 



This hypothesis has not yet been advanced, but hke the preceding, it 

 would receive no support from the facts. 



C. It is an enzyme, normally elaborated by the bacterium. This 

 enzyme can not be a normal autolysin. Among other objections, bac- 

 teriophagy, as is recognized even by those who support this hypothesis, 

 has none of the appearances of an "autolysis," the characteristics of the 

 two are even exactly opposed. This anomaly needs explanation if 

 they would have us accept this view. 



The principal argument advanced to support this hypothesis is the 

 presence of a bacteriophage principle in cultures of some bacterial 

 strains. This fact is in no way contradictory to the hypothesis of the 

 living nature of the bacteriophage. Nature presents us with abundant 

 evidence in the innumerable examples of such symbioses. Further- 

 more, the fact that it is possible to purify "lysogenic" strains shows 

 that the bacteriophage behaves just as does any abnormal "con- 

 tamination." 



Finally it is possible to prove that the normal autolysin contained in a 

 bacterium can not be the bacteriophage. 



Since experiment shows that the bacteriophage principle is not a 

 normal autolysin, the autolytic hypotheses of bacteriophagy are auto- 

 matically excluded. 



D. It is a living principle, existing normally in the bacterium. From 

 the moment when experiment demonstrated that the bacteriophage prin- 

 ciple is not contained in the normal bacterium this theory becomes as 

 unfounded as the preceding. Furthermore, the experimental data 

 presented in the next chapter will show the inadmissibility of this 

 theory, as well as the deficiencies of the preceding. 



III. The bacteriophage is a living being foreign to the bacterium. 

 This is the sole hypothesis which is not in contradiction with any of the 

 experimental facts of bacteriophagy. It is the only hypothesis which 

 provides rational explanation of all of these facts, without necessitating 

 recourse to any other hypothesis. 



It is, therefore, the most probable hypothesis; the only one which 

 takes into account all of the facts. 



