CHAPTER IV 



THE MANNER OF THE GRADUAL 

 CHANGE OF GENES 



1. The Explanation of the Biogenetic Law or the 

 Theory of Recapitulation 



The biogenetic law or the theory of recapitulation states that each 

 organism tends in its individual life history (ontogeny) to recapitulate 

 various states through which its ancestors have passed in their racial 

 history (phylogeny). This law or the theory should be expected from 

 the above concept that the germ cells are the reductive form of the 

 somatic and that the change is reversible. 



To begin with, we shall consider of the case of primitive unicel- 

 lular organisms such as Sporozoa. If a primitive organism like Sporo- 

 zoa is brought under a certain environment, the structure of the cell 

 may be changed to produce spores, whereas this latter can recover the 

 original cell structure if the environment is again properly changed. 

 Since the structure of protoplasm is always governed by the elemen- 

 tary bodies, rich in nucleic acid, also the change between the cell and 

 the spore must be subjected to such elementary bodies, which can 

 be looked upon as the genes. Thus, the change can be expressed as 

 A:;^B, in which A is the structure of the gene of the cell and B that 

 of the spore. 



Now, if this primitive organism advances to have A^-structure, 

 the change is : A->A\ Since the evolution of both morphological and 

 functional characters of an organism is given rise to by the advance- 

 ment of gene structure, the advancement of the gene structure from 

 A to A^ should be accompanied by the evolution of the characters 

 of the organism corresponding to the structural advancement in the 

 gene. 



On the other hand, as the genes possess the structural reversi- 

 bility, when A^ is reduced to B-structure of the spore, or of the germ 

 cell, it must take the course : A^->-A->-B, whereas when B is developed 

 to A^ the course should be : B^A->A\ This course is to be repeated 

 in every change from the adult form to the spore, or the germ cell, 

 and from the latter to the adult form. Through this repetition the 



