GENERAL CONSIDERATIONS AND CONCLUSIONS 29 1 



In this whole question there is danger of extending our own expe- 

 rience as agents in the constructing of products useful to ourselves, to 

 the organic world, in attempting to account for the way in which the 

 useful characters of organisms have arisen. We see a ship being 

 built, and we know that when it is finished it will be useful. We 

 explain its building by its future usefulness, that is, we explain the 

 process as the result of human teleology. But have we any right to 

 extend this principle to the organic world, and infer that processes are 

 there carried out because they will ultimately be useful to the individual 

 in which they take place ? Unconsciously we have shifted our point of 

 view. The ship does not build itself, and the final result of the build- 

 ing is of no use to the ship. On the contrary, the organism does 

 build itself and the result is useful only to itself. Unless we suppose 

 that some external agent acting as we do ourselves directs the 

 formative processes in animals and plants, we are not justified in 

 extending our experience as directive agents to the construction of 

 the organic world ; and if we are not justified in drawing such a con- 

 clusion, since the organism by no means always responds adaptively, 

 and in many cases very badly and incompletely, then, it seems to me, 

 we must look for another point of view. 



In connection with his work on the regeneration of the eye of the 

 salamander, Gustav Wolff ('93) has made some sweeping statements 

 in regard to the phenomenon of adaptation. " Purposeful adaptation 

 is that which makes the organism an organism. It is this adaptation 

 that appears to us as the most characteristic property of all living 

 things. We can think of no organism without this characteristic." 

 In another place he states, "... we recognize that every explana- 

 tion that presupposes the living being, every post-vital explanation of 

 organic adaptation, presupposes in every case that which it attempts 

 to explain ; we recognize that the explanation of adaptation must co- 

 incide with the explanation of life itself." There is, perhaps, some 

 truth in this statement, but, on the other hand, Wolff has, I think, 

 shot somewhat over the mark. As Fischel (1900) has pointed out, 

 the response is sometimes not adaptive, as when two lenses develop 

 in the same eye in the salamander ; and, we may add, as when an an- 

 tenna develops in certain Crustacea in place of an eye, or as when a 

 tail develops instead of a head, or a head in place of a tail. In the 

 light of these facts, it is, I think, going too far to assert that the power 

 of living things to respond adaptively to changes in themselves or in 

 their environment is synonymous with life itself. All that we can 

 fairly claim is that in several cases living forms have been shown to 

 be able to complete themselves, and this may be interpreted as an adap- 

 tive response. It would carry us far beyond the scope of the present 

 volume to discuss the question of adaptation in general, and I think it 



