134 III. THE EVOLUTION OF VIRUSES 



or in the cell itself, since even in its fragments, i. e., in the virus-like 

 particles, the faculty can be proved. Smith (9) stated that non-lysogenic 

 strain can be changed lysogenic through the incubation with the lyso- 



Lysogenic Non-lysogenic Bacterium changed 



bacterium susceptible bacterium into lysogenic 



Phage particle Phage particle 



Fig. 16. The change of phage-susceptible bacterium into lysogenic 

 by the phage produced by a lysogenic strain. 



genie strain ; this change may not necessarily be ascribed to the action 

 of phage freed from the lysogenic strain, because such a change should 

 naturally to be expected in the interaction between two different strains 

 without any participation of virus-like particulate agents. 



If the above conception as regards lysogenic strains is correct, 

 every strain of bacteria may be lysogenic to strains having weaker 

 assimilase actions than it, provided that the mutual combination be- 

 tween them is established. Roustree (10) has proved that 27 out of 30 

 strains of staphylococci which have been chosen arbitrarily are lyso- 

 genic, and she stated that also with the remaining three strains lyso- 

 genicity may be proven if suitable indicator strains are found. 



Such a phenomenon may not be confined to bacteria. If particles 

 or fragments of the protoplasm of some animal cells can combine with 

 certain bacterial protoplasm of weaker assimilase action the particles 

 may be able to act as a phage upon the bacteria. The phage found in 

 animal feces may belong to this category. 



In this connection, however, a serious question may arise as regards 

 the establishment of the combination between the two different cell 

 protoplasm, since there should exist in a virus a structure which cor- 

 respond to a structure of the host cell protoplasm for the establishment 

 of the combination between the virus and the host cell. The relationship 

 in the structures between a virus and the host protoplasm may be 

 analogous to that existing between an enzyme and the substrate. Viruses 

 can combine with host cells through such a structure, and after the 

 combination, structures in the virus not in conformity with those of 

 the protoplasm exert their action to rearrange the protoplasm structure. 



Since the structure causing the combination distributed between a 

 virus and the host protoplasm must be present, in general, between two 

 protein molecules of a similar kind as already discussed in detail in 

 Part II, a certain strain of bacteria can act as lysogenic upon a certain 



