204 THE THEORIES OF EVOLUTION 



tion ; but for the transmission of characters, evolution 

 would be incomprehensible ; either acquired characters 

 can be transmitted hereditarily or there is no evolu- 

 tion. 



The question may be asked: what are the facts 

 which prove the heredity of acquired characters? 

 Since many organic modifications are hereditary we 

 may logically answer that any modification may be- 

 come hereditary. Those who contend that only cer- 

 tain modifications are hereditary are then welcome to 

 bring proof. It is true that not every acquired char- 

 acter is inherited, but this is due to the fact that the 

 farther back a character goes, the more deeply rooted 

 it is, and that the more recently it has been acquired, 

 the more easily it may disappear. This is why a char- 

 acter which has persisted for many generations is 

 more likely to be inherited, while a character of recent 

 origin disappears more quickly. 



Spencer cites many cases which cannot be explained 

 by natural selection nor by panmixia and in which the 

 heredity of acquired characters must be the only fac- 

 tor. Take for instance the origin of the lingual 

 papillae. They have multiplied not because they are 

 useful or necessary to life but because the tongue, 

 during the process of speech or mastication, constantly 

 comes in contact with various points of the oral cavity. 

 The distribution of tactile discriminativeness on the 

 surface of the bod}*- shows that tactile corpuscles are 



