414 



SCIENTIFIC THOUGHT. 



contemplation of the result may permit us to trace 

 backward the process by which it was brought about ; 

 but we are not warranted in assuming that it existed 

 independently, like the plan of a building or the purpose 

 of an instrument. In the place of a growth according to 

 a prearranged plan, Darwin put the conception of an 

 automatic adjustment called " natural selection " ; in the 

 place of a conscious end or purpose he put the concep- 

 tion of a mere result, a product, the " surviving fittest." ^ 

 The development and proof of Darwin's ideas gave a 

 new impetus to biological research, as it did also to the 

 science of the history and economy of nature. The fact 

 that the phenomenon of selection, or rather of automatic 

 crowding out, presupposes intimate relations and contact 

 of every living thing with numberless other similar and 

 dissimilar beings, led naturalists into the open air, to 



^ A very full appreciation of the 

 great chanf^e that has come over 

 the sciences of nature through the 

 influence of Darwin will be found 

 in the various wiitings and ad- 

 dresses of Prof. Haeckel, ncjtablj' 

 in his address to the German As- 

 sociation in 1877 at Munich, " Ueber 

 Entwickelungslehre " (repj-inted in 

 ' Gesaminelte popuUire Vtjrtrage,' 

 vol. ii. ]). 97). A more critical exam- 

 ination, referring specially to the 

 central biological problems, is the 

 address by Du Bois-Reymond, de- 

 livered in 1876 in the Berlin Acad- 

 emy, and reprinted in ' Heden,' vol. 

 i. p. 21], with valuable literary 

 notes. He there discusses how far 

 the principle of natural selection, 

 in addition to the general doctrine 

 of descent, has been adopted or op- 

 posed, and refers to the outstand- 

 ing difficulties. " One of the great- 

 est difficulties,"' he .says (p. 226), 

 " presents itself in phj'siology in the 



so-called regenerative power, and — 

 what is allied to it — the natural 

 power of healing : this may now be 

 seen in the healing of wounds, in 

 tlie delimitation and compensation 

 of morbid processes, or, at tlie 

 farthest end of the series, in the 

 re -formation of an entire fresh- 

 water polyp out of one of the two 

 halves into which it had been 

 divided. This artifice could surely 

 not have been learnt by natural 

 selection, and here it ajjpeai's im- 

 possible to avoid the assumption of 

 formative laws acting for a pur- 

 p<i.se. The}' do not become moi-e 

 intelligible by the fact that the 

 regeneration of mutilated crystals, 

 observed by Pasteur and others, 

 points to similar proce.sses in inani- 

 mate nature. Also the ability of 

 organisms to perfect themselves by 

 exercise has not found sufficient 

 appreciation with regard to natural 

 selection." 



