1899] THE SCOPE OF NATURAL SELECTION 125 



of one variation happen to be present at one and the same time. His 

 difficulty therefore does not appear to me to be answered by Wallace. 



Weismann, 1 admitting the objection of Spencer's as having a real 

 existence, attempts to answer it by the tendency of natural selection 

 itself to induce definite variability. This answer does not seem to 

 me to be much more satisfactory than Wallace's, for the point of the 

 argument is, that as the accessory variations are necessary to the proper 

 working of the primary they must be present from the first selection, and 

 as determinate selection can only appear after selection has been con- 

 tinued for some generations it must be unable to explain this occurrence 

 of co-ordinated parts which occurs prior to the action of selection. 



Mr. Lloyd Morgan in the December number of Natural Science 

 deals with this difficulty in a manner which appears to me to be much 

 more satisfactory. We have seen in the brief summary of his views 

 that he draws an important distinction between somatic response to 

 environment and the selection of germinal variations, that under 

 altered conditions of environment he considers somatic plasticity to 

 be one of the principal determining causes of selective preservation, 

 and as he admits the action of use -modification on the somatic 

 structures, those organisms whose somatic structures are sufficiently 

 plastic to allow of this newer co-adjustment to the newer conditions 

 will survive on account of their plasticity, and this will continue to 

 happen over one or more generations until chance variations happen 

 to make their appearance in the same direction as the environment, 

 then the offspring of this organism or these organisms will start life 

 with a slight favourable predisposition to their environment, which in 

 addition to somatic plasticity will give them a slightly better chance 

 than those without this predisposition, hence by the fostering power 

 of body response a co-ordinate structure might be formed through 

 cumulative co-incident variability. This objection therefore does not 

 apply to the theory of Natural Selection modified as above. 



Keeping in view this theory of co-incident variability, there is 

 another consideration which will also tend to weaken this objection. 

 As selection must be from the first organismal, and as adaptation to 

 climatic conditions must be absolute, as far as it is capable of exercis- 

 ing a selective action, a certain common tendency will be present in 

 all more or less similar organisms living under these more or 

 less similar physical conditions. This primitive climatic basis will 

 give a certain direction to the subsequent inter-organismal selection, 

 and we have seen that with progressive evolution the necessary 

 specialisation entails an increasingly definite tendency in the organism 

 as a whole, owing to the increasing dependence of one part on another : 

 hence it will follow that all variations will tend to become increasingly 

 co-ordinated as they become increasingly specialised, and they will also 

 become increasingly so as we pass from the lower to the higher forms. 



1 " Germinal Selection." 



