68 Darwin, and after Darwin. 



through the blending of variations each of which 

 has always been in itself of adaptive value. 



From this I hope it will be apparent that the only 

 way in which the " difficulty " from co-adaptation can 

 be logically met by the ultra-Darwinian school, is by 

 denying that the phenomenon of co-adaptation (as 

 distinguished from the blending of adaptations) is ever 

 to be really met with in organic nature. It may be 

 argued that in all cases where co-adaptation appears 

 to occur, closer examination will show that the facts 

 are really due to a blending of adaptations. The 

 characters A + B + C + D, which are now found united 

 in the same organism, and, as thus united, all conspiring 

 to a common end. may originally have been distri- 

 buted among different organisms, where they severally 

 subserved some other ends or possibly the same 

 end, though in a less efficient manner. Obviously, 

 however, in this case their subsequent combination 

 in the same organism would not be an instance of 

 co-adaptation, but merely of an advantageous blend- 

 ing together of already existing adaptations. This 

 argument, or rejoinder, has in point of fact been 

 adopted by Professor Meldola, he believes that all 

 cases of seeming co-adaptation are thus due to a 

 mere blending of adaptations 1 . Of course, if this 

 position can be maintained, the whole difficulty 



1 Nature, vol. xliii. pp. 410, 557 ; vol. xliv. pp. 7, 29. I say 

 "adopted," because I had objected to his quoting the analogy of artificial 

 selection, and stated, as above, that the only way to meet Mr. Spencer's 

 " difficulty " was to deny the fact of co-adaptation as ever occurring in 

 any case. It then appeared that Professor Meldola agreed with me as to 

 this. But I do not yet understand why, if such were his view, he began 

 by endorsing Mr. Wallace's analogy from artificial selection i. e. 

 confusing the case of co-adaptation with that of the blending of adapta- 

 tions. If any one denies the fact of co-adaptation, he cannot assist his 



