it8 / LIONEL TAYLER [august 



tends to develop and maintain its own structure, (2) it tends to 

 reproduce, under suitable conditions, other organisms more or less 

 similar to itself. We have therefore to consider every living form 

 from a somatic and a germinal side. Both somatic and germinal aspects 

 exhibit two tendencies which are differently proportioned in different 

 organisms, (1) to remain constant in spite of variable external con- 

 ditions, (2) to manifest certain changes of structure. According as 

 one or other of these tendencies predominate the organism will 

 develop and reproduce definitely or indefinitely. In both somatic and 

 germinal development natural selection will tend to favour the 

 requisite definiteness or indefiniteness of structure. The inheritance 

 of somatic characters does not appear to have been established in any 

 one of the many alleged examples ; the evidence, therefore, that up to 

 the present time has been collected, would seem to favour the con- 

 clusion that if accommodations are ever inherited it is an event of 

 extreme rarity. 



Yet in spite of the lack of evidence in support of the inheritance 

 of acquired characters, there seems to be a considerable mass of 

 evidence in favour of the contention that germinal variations often 

 correspond in their tendencies to somatic accommodations. 



Definite variability corresponding to environmental accommodation 

 might however be acquired in the following way. It has already been 

 noticed that every organism, both from its somatic and germinal 

 aspects, exhibits two tendencies, one towards definiteness, the other 

 towards indefiniteness ; somatic indefiniteness appears to be able to be 

 modified by environmental influences, therefore those organisms whose 

 somatic tendency is predominantly plastic will survive under altered 

 conditions of environment where those organisms of a less easily 

 modifiable tendency will be eliminated. Now if somatic characters 

 rarely or never become germinal, the modifications of the parental 

 organisms cannot be transmitted to their offspring, but those offspring 

 that happened to be endowed with variations in the same direction as 

 the acquired but not transmitted modifications, would start their life 

 with a predisposition favourable to their environment, and therefore 

 favourable to more complete modification of the somatic side of the 

 organism ; this tendency being accumulative under constant conditions, 

 coincident variability would arise by the process of selective elimina- 

 tion and preservation, without the need for the assumption of use- 

 inheritance, which assumption facts appear to negative. 



Coincident variations would thus have a better chance of survival 

 simply because they would be present in the surviving organisms, but 

 the principle of selection would be the same whether the variations 

 were coincident or not. 



It follows from the preceding argument that definite variability 

 is a logical necessity, under certain conditions, if the principle of 

 natural selection be allowed to be a factor of considerable importance 



