LECTURE III 



NATURE AND NURTURE 



This chapter, which all who have attended my lectures during 

 the last ten years will find familiar, does not deal with the inter- 

 minable question whether ** acquired characters" are inherited, but, 

 granting that this may be the case, it is an attempt to weigh the 

 value of this "factor" in natural history. 



Herbert Spencer tells us that the segmentation of the backbone 

 is the inherited effect of fractures, caused by bending, but Aristotle 

 has shown ("Parts of Animals," I. i.)that Empedocles and the ancient 

 writers err in teaching that the bendings to which the backbone 

 has been subjected are the cause of its joints, since the thing to 

 be accounted for is not the presence of joints, but the fitness of 

 the joints for the needs of their possessor. 



It is an odd freak of history that we of the end of the nine- 

 teenth century are called upon to reconsider a dogma which was 

 not only repudiated two thousand years ago, but was even then 

 called antiquated. "Is there anything whereof it may be said : 

 See ! this is new ? It hath been already of the old time which 

 was before us." 



In this day of laboratories, are we not in danger of forgetting 

 the first principle, so clearly put by Aristotle-, that the thing to 

 be explained is not the structure of organisms, but the fitness of 

 this structure for the needs of living things in the world in which 

 they pass their lives.!* We must be on our guard lest the great 

 discovery that protoplasm is the physical basis of life obscure the 

 truth that what Huxley has called the physical basis is one thing, 

 while what Aristotle has called the essence of life is quite another 

 thing. The physical basis of a locomotive engine is the expan- 

 sion of steam, but its essence is fitness for the service of man. 

 E 49 ^ 



