EXAMINATION OF THE THEORIES OF OTHER WRITERS. 2G9 



changed instincts of the woodcock ; and the effects of blend- 

 ing instincts by crossing. 



It having been fully shown by these selected examples 

 that instincts may arise by natural selection alone, or by 

 lapsing intelligence alone, the discussion went on to show 

 that instincts in general are not necessarily confined to one 

 or other of these two modes of origin ; but, on the contrary, 

 that these principles when working in cooperation have 

 greater influence in evolving instincts than either of them 

 can have when working singly. For, on the one hand, 

 hereditary proclivities or habitual actions which, being useful 

 though never intelligent, were originally fixed by natural 

 selection, may come to furnish material for further improve- 

 ment, or be put to better uses, by intelligence ; and, con- 

 versely, adjustments originally due to lapsed intelligence may 

 come to be greatly improved, or put to better uses, by natural 

 selection. For, taking the latter case alone, if, as we have 

 seen, intelligent actions may by repetition become automatic 

 as secondary instincts, and if they may then vary and have 

 their variations fixed in beneficial lines by natural selection, 

 how much more scope may be given to natural selection in 

 this further development of an instinct, if the variations of 

 this instinct are not wholly fortuitous, but arise as intelligent 

 adaptations of ancestral experience to the perceived require- 

 ments of individual experience. Clearly, natural selection 

 most in such a case be winking at a much greater advantage 

 than it does when working alone in the formation of primary 

 instincts, where it is supplied only with fortuitous variations, 

 instead of with variations which, being determined by intelli- 

 gence, are from the first adaptive. And no less clearly, the 

 principle of Lapsing intelligence mnsl he working at a much 

 greater advantage when thus in associal ion with natural selec- 

 tion, than it is when working alone in the formation of 

 secondary instincts ; for natural selection in this case must 

 always tend to favour the best of the intelligent adjustments, 

 and by concentrating the power of heredity into them must 

 tend the more speedily to render them automatic or in- 

 stinctive. 



It is of no moment, b i regards instincts of blended origin, 

 to determine in particular cases which of the two principles 

 —natural selection or lapsing intelligence — has had the 



