396 V. THE NATURE OF EVOLUTION 



if its transmission to the progeny is possible unless it is repeatedly 

 engraved by infection. 



The Lamarckian theory of the inheritance of acquired characters 

 is not generally accepted because of the failure to secure any definite 

 evidence for the theory. However, since the change of the genes is 

 reversible, the evidence demanded has never been, and will never be, 

 obtained. The organism can develop a new character under a new 

 environment, but, when it is returned to the original environment, the 

 change is not lasting. For the continuance of a new character, the 

 new environment inducing the new character is always needed, and 

 in so far as the new environment continues to exist, the new character 

 is not only lasting but also will gradually be stabilized. 



Here we should remind the most remarkable character of proteins 

 already discussed. Namely, proteins can recover their previous struc- 

 ture, because the previous structure is remaining in their memory, 

 but if it is forgotten the recovery will become impossible. This very 

 forgetting is to occur when proteins exist for prolonged period away 

 from the previous pattern. Therefore, a new character produced under 

 a new environment will be fixed when the new environment becomes 

 constant, and as a result the character will not to be lost so soon 

 even when the organisms are removed to the previous environment. 



Thus adapted characters of organisms to environmental factors, 

 such as temperature, light, and nutrition, will not only remain in 

 existence as long as the factor continues to exist, but will be 

 gradually stabilized in being accumulated little by little in the genes, 

 until the acquired pattern becomes the ordinary one with the oblivion 

 of the previous pattern. 



If an environmental factor is again altered in a new direction 

 after the former pattern has been forgotten or the return of the former 

 pattern has become difficult, then adaptive change will begin anew on 

 the basis of this acquired pattern, without returning to the previous 

 one. In such a way the pattern of the genes will continuously ad- 

 vance leading to the evolution of the organisms. Newly formed 

 pattern is always unstable, and so the isolation is indispensable for 

 the evolution. 



In the case of individual development or ontogeny, as previously 

 stated, newly formed structures are likewise unstable, but they will 

 gradually become stable and irreversible as a result of the oblivion 

 of former structures. Also in this respect, ontogeny recapitulates 

 phylogeny. 



In short, it may be concluded that the oblivion of the former 

 structure is necessary for the evolution. However, for the function 

 of the germ cell to recapitulate the phylogeny, an extremely strong 



