74 Darwin, and after Darwin. 



Now, if all these distinctions between the Dar- 

 winian and Lamarckian principles are valid — and 

 I cannot see any possibility of doubt upon this point 

 — strong evidence in favour of the latter would be 

 furnished by cases (if any occur) where structures, 

 actions, instincts, &c., although of some adaptive 

 value, are nevertheless plainly not of selective value. 

 According to the ultra-Darwinian theory, no such 

 cases ought ever to occur : according to the theory 

 of Darwin himself, they ought frequently to occur. 

 Therefore a good test, or criterion, as between these 

 different theories of organic evolution is furnished by 

 putting the simple question of fact — Can we, or can 

 we not, show that there are cases of adaptation where 

 the degree of adaptation is so small as to be incom- 

 patible with the supposition of its presenting a selective 

 value ? And if we put the wider question — Are there 

 any cases where the co-adaptation of severally useless 

 parts has been brought about, when even the re- 

 sulting whole does not present a selective value? — 

 then, of course, we impose a still more rigid test. 



Well, notwithstanding the difficulty of proving such 

 a negative as the absence of natural selection where 

 adaptive development is concerned, I believe that there 

 are cases which conform to both these tests simul- 

 taneously ; and, moreover, that they are to be found in 

 most abundance where the theory of use-inheritance 

 would most expect them to occur — namely, in the 

 province of reflex action. For the very essence of 

 this theory is the doctrine, that constantly associated 

 use of the same parts for the performance of the same 

 action will progressively organize those parts into 

 a reflex mechanism— no matter how high a degree of 



