XXV.] GENERAL REJIAEKS ON DEVELOPMENT OF SPECIES. 337 



purely physical process, a case of purely physical causa- 

 tion ; but I have given reasons, which to my mind are 

 conclusive, against accepting natural selection as an 

 explanation of the complexities of organic structure. But 

 I believe that these physical agencies, self-adaptation and 

 natural selection, are what produce organization, and are Self- 

 the operative causes of progress in organization ; not, fs'^gu-^ecr 

 however, acting alone, but under the guidance of intelli- by intelli- 

 gence. I believe that intelligence guides the process of ^^'^'^^* 

 self-adaptation, producing adaptations which no unintelli- 

 gent process could produce. I have no doubt the law of 

 natural selection is universally operative, in this sense, that 

 natural selection by "survival of the fittest"^ in the 

 struggle for existence is the reason why new and improved 

 races, when once formed, supersede the old and unimproved 

 ones; but I have stated my reasons for believing that 

 spontaneous variation alone can never produce any com- 

 plex organization. I believe that intelligence determines Intelli- 

 those variations to occur together which are needed together, determines 

 To return to a former instance : — If I am right, such an co-ope- 

 organ as the eye has been formed by a series of gradual varktions 

 successive improvements, in each of which those different ^° °°°™ 



f o togetner. 



variations m the different parts of its complex structure 



which are necessary to make one another useful have been 

 determined to occur together by the mysterious power of 

 unconscious organic intelligence. But every improvement, 

 when once made, has been preserved, perpetuated, and 

 multiplied by the action of natural selection. 



I believe that organizing intelligence co- exists and co- lutelli- 

 operates with the unintelligent forces through all life ; but mostVomi- 

 that intelligence is most completely dominant in the highest i^p* '^ the 

 life. It is where intelligence is most completely dominant ufe. 

 that, as we have seen, organic progress is most rapid ; 

 though there is least spontaneous variation among the 

 most highly organized forms, and consequently it is among 

 them that the least could be done by mere natural selec- 

 tion among unguided spontaneous variations.^ And it is 



1 This expression is used in Spencer's Principles of Biology. 

 "- See p. 333. 



