Ko. 642] VARIATION IN INDIVIDUAL GENE 



35 



that case the gene itself would only initiate and guid^ the 

 direction of the reaction. On the other hand, the extreme 

 alternative to such a conception has been generally as- 

 sumed, perhaps gratuitously, in nearly all previous 

 theories concerning hereditary units ; this postulates that 

 the chief feature of the autocatalytic mechanism resides 

 in the structure of the genes themselves, and that the 

 outer protoplasm does little more than provide the build- 

 ing material. In either case, the question as to what the 

 general principle of gene construction is, that permits 

 this phenomenon of mutable autocatalysis, is the -most 

 fundamental question of genetics. 



The subject of gene variation is an important one, 

 however, not only on account of the apparent problem 

 that is thus inherent in it, but also because this same 

 peculiar phenomenon that it involves lies at the root of 

 organic evolution, and hence of all the vital phenomena 

 which have resulted from evolution. It is commonly 

 said that evolution rests upon two foundations — inher- 

 itance and variation ; but there is a subtle and important 

 error here. Inheritance by itself leads to no change, and 

 variation leads to no permanent change, unless the varia- 

 tions themselves are heritable. Thus it is not inheritance 

 and variation which bring about evolution, but the in- 

 heritance of variation, and this in turn is due to the 

 general principle of gene construction which causes the 

 persistence of autocatalysis despite the alteration in 

 structure of the gene itself. Given, now, any material 

 or collection of materials having this one unusual char- 

 acteristic, and evolution would automatically follow, for 

 this material would, after a time, through the accumula- 

 tion, competition and selective spreading of the self- 

 propagated variations, come to differ from ordinary in- 

 organic matter in innumerable respects, in addition to 

 tlie original dift'oronce in its mode of catalysis. There 

 would thus result a wide anp l)t'r\vi"eii this matter and 

 other matter, wliirh w^uild k.-cp urowiug wider, with the 

 increasing complexity, diversity and so-called ''adapta- 

 tion " of the selected mutable material. 



