INADEQUACY OP NATURAL SELECTION, ETC. G15 



selected varieties of pigeons is lost ; the fact that lack of con- 

 comitance in decrease of jaws and teeth in sundry kinds of pet 

 dogs, has caused great crowding of the teeth (" The Factors of 

 Organic Evolution, Essays, i, 401-402). And I then argued that 

 if co-operative parts, small in number and so closely associated as 

 these are, do not vary together, it is unwarrantable to allege that 

 co-operative parts which are very numerous and remote from one 

 another vary together. After making this rejoinder I enforced 

 my argument by a further example that of the giraffe. Tacitly 

 recognizing the truth that the unusual structure of this creature 

 must have been, in its most conspicuous traits, the result of sur- 

 vival of the fittest (since it is absurd to suppose that efforts to 

 reach high branches could lengthen the legs), I illustrated afresh 

 the obstacles to co-adaptation. Not dwelling on the objection 

 that increase of any components of the fore-quarters out of 

 adjustment to the others, would cause evil rather than good, I 

 went on to argue that the co-adaptation of parts required to 

 make the giraffe's structure useful, is much greater than at first 

 appears. This animal has a grotesque gallop, necessitated by the 

 great difference in length between the fore and the hind limbs. 

 I pointed out that the mode of action of the hind limbs shows 

 that the bones and muscles have all been changed in their propor- 

 tions and adjustments ; and I contended that, difficult as it is to 

 believe that all parts of the fore -quarters have been co-adapted 

 by the appropriate variations, now of this part now of that, it 

 becomes impossible to believe that all the parts in the hind- 

 quarters have been simultaneously co-adapted to one another and 

 to all the parts of the fore-quarters : adding that want of co- 

 adaptation, even in a single muscle, would cause fatal results 

 when high speed had to be maintained while escaping from an 

 enemy. 



Since this argument, repeated with this fresh illustration, was 

 published in 1886, I have met with nothing to be called a reply ; 

 and might, I think, if convictions usually followed proofs, leave 

 the matter as it stands. It is true that, in his Darwinism, Mr. 

 Wallace has adverted to my renewed objection, and, as already 

 said, contended that changes such as those instanced can be ef- 

 fected by natural selection, since such changes can be effected by 

 artificial selection : a contention which, as I have pointed out, 

 assumes a parallelism that does not exist. But now, instead of 

 pursuing the argument further along the same line, let me take 

 a somewhat different line. 



If there occurs some change in an organ, say by increase of its 

 size, which adapts it better to the creature's needs, it is admitted 

 that when, as commonly happens, the use of the organ demands 

 the co-operation of other organs, the change in it will generally 



