THE STRONGEST EVIDENCE OF ALL 73 



developing under the influence of nutriment has been displaced in 

 him by that of developing under the stimulus of use. For example, 

 the ability to run and swim instinctively is so general amongst the 

 lower mammalia that there can be little doubt that the ancestors 

 of man formerly possessed, but subsequently lost, this power. 1 



115. Here, indeed, we have the strongest evidence of all against 

 the Lamarckian hypothesis. When we find it impossible to 

 formulate a probable hypothesis as to how acquirements can be 

 transmuted into inborn characters, or to conceive by what process, 

 short of miracle, the power of thus transmuting them can have 

 been evolved, it becomes necessary to ask for very strong and 

 unequivocal evidence of the alleged transmutation. When we 

 ascertain by a rigorous deductive inference of consequences that 

 the hypothesis is apparently incompatible with the fact that life 

 exists and is adapted to its surroundings, our reasons for rejecting 

 it are greatly strengthened. The only doubt that remains is as to 

 whether, in spite of all our testing, we have reasoned correctly. 

 But when we find that the whole course of evolution has been such 

 that, so far from ' inborn ' characters tending to replace ' acquire- 

 ments,' the reverse has constantly happened[; when we find that the 

 human being, for example, has lost so much that was inborn in his 

 remote ancestors, that he has become incapable of reaching 

 maturity except under the stimulus of use, all doubt vanishes. 

 The appeal to reality then furnishes decisive proof. Having 

 regard to the facts, a supposition directly contrary to the 

 Lamarckian hypothesis (viz., a supposition that inborn characters 

 tend to be transmuted into acquirements) may perhaps be main- 

 tained with some appearance of probability. But a supposition 

 that acquirements tend to be transmuted into innate characters is 

 very obviously in conflict with what has occurred in nature. 2 



116. Though the Lamarckian doctrine is abandoned by nearly 



1 See 673. 



2 Most biologists, I think, reject, or rather believe that they reject, the 

 Lamarckian doctrine on grounds furnished by experiment. I have heard (so 

 very odd, occasionally, are the notions of scientific men concerning science) all 

 other evidence and reasoning, all attempts to establish a chain of causation and 

 make biology, like physics and mathematics, a deductive science, denounced as 

 ' weak.' But it appears to me that the experimental evidence is strongly in favour 

 of the, at any rate, ' faint and fitful ' transmission of acquirements, a transmission 

 which, if sufficiently general, would inevitably lead to racial change. We cannot 

 disprove a statement that an event sometimes happens by proving that some- 

 times it does not happen. One positive example outweighs a hundred negative 

 instances, and Brown Sequard, Romanes, and numbers of other observers have 

 recorded, or thought they recorded, many. To this day French observers, 

 especially French medical men, frequently announce such experiments as the 



