368 THE NATURE OF EVOLUTION 



reversible course will become a beaten track ; in other words, the 

 memory of the course will be held completely by the repetition as dis- 

 cussed in Chapter I of this Part. Since the memory is a type of the 

 structural pattern of the gene, it should be inherited generation after 

 generation. 



If the organism evolves further and advances successively" to A", 

 -A^, and so on, the course will become longer and longer, but as the 

 repetition is to be continued without stopping, the track continuously 

 being beaten and the memory is as sure as ever. In such a manner, 

 the organism can evolve upto an extremely high state as A" . Even 

 in this case, in its reduction to the germ cell, it must take the course : 



A"^ A"-^ A^->A"->A^-vA->B ; and B, the germ cell, must take the 



entirely reverse course in its development to A" . It is impossible to 

 take another course. Thus, the germ cell must take the course of 

 phylogeny when it develops into the adult form. 



2. The Liberation of Active Groups 



Proteins may consist of two types of structures, one of which is 

 stable back-bone structure and the other may be involved in polar 

 forces in side chains which are to be liberated by the unfolding of 

 polypeptide chains. There are numerous evidences that each of two 

 structures determines each different character of the proteins (71). For 

 instance, as already discussed, immunological character of viruses is 

 determined by the stable back-bone structure, while virus action 

 cannot be developed without the labile structure. 



In a similar way, the manner of changes in the genie structure 

 governing both ontogeny and phylogeny may also consist of two types 

 due to these two structures. The main change of chief importance may 

 be involved in back-bone structure, but the development of some func- 

 tional and morphological character responding to the back-bone pattern 

 may not take place without the transient, unstable structure. 



This view is supported by the following fact : Lysogenic bacteria 

 do not liberate phage by a mere disruption, while an adequate change 

 in their environmental conditions, for example, irradiation with ultra- 

 violet light results in phage production (56). And the susceptible 

 Tbacteria infected with this virus become lysogenic and at the same 

 time resistant to the phage, but usually they do not produce the virus 

 unless proper stimuli are given. This fact can be readily explained 

 Ijy the assumption that the virus consists of two types of structures, 

 -Stable and unstable. Namely, bacteria may acquire the immunity 

 against a phage following the infection with the virus, because they 



