Hi THE DARWIN CENTENARY. [Februarys, 



liability to injury. Other contingent, individual adaptations of a 

 still more striking kind are found in the acclimatization of organisms 

 to certain poisons, particularly bacterial poisons and snake venom. 

 It has been shown that, as an antidote to these toxins, various anti- 

 toxins are formed, and for every toxin, or at least for every tox- 

 albumen its own particular anti-body. Now many of these poisons 

 are of such a sort that it is perfectly certain that the immediate 

 ancestors of the forms poisoned could never have experienced them, 

 and yet the response is as perfect as it could be if it had been due 

 to long experience. Many other similar cases might be cited if 

 time allowed, but these are enough. The apparently intelligent and 

 purposive response of an organism to a stimulus or environment 

 which it has never experienced before is one of the most mysterious 

 and fundamental problems of biology. 



There are, therefore, adaptations which neither Lamarckism nor 

 Darwinism nor any other system so far proposed can explain satis- 

 factorily, and this has led several biologists, notably Wolff and 

 Driesch, to the conclusion that these theories " fail all along the 

 line." But this conclusion appears to me hasty and extreme. There 

 are many adaptations, as we have seen, which may be beautifully 

 explained by the Darwinian theory, viz., all racial or inherent adap- 

 tations which are not first called forth by the contingent stimulus to 

 which they are the appropriate and useful response. On the other 

 hand adaptations of the latter sort are problems of physiology rather 

 than of phylogeny. One of the greatest needs of biology is for 

 more detailed and accurate information regarding them ; we must 

 know exactly what happens in each case, the physiology of the 

 response irrespective of its usefulness, and then perhaps the latter 

 may find an explanation. It is certainly premature to abandon 

 hope of finding a natural and causal explanation of such phenomena, 

 as Driesch and Wolff do, before we are really acquainted with the 

 phenomena themselves. 



Some of these contingent adaptations probably belong to the 

 fundamental and original properties of living things and as such 

 are not to be explained by any theory of evolution ; for it must not 

 be forgotten that organic evolution is a theory of transmutation 

 which undertakes primarily to explain the diversity which exists 



