ORGANIC EVOLUTION — MENTAL 163 



which all young mammals instinctively indulge are 

 obviously adapted to this end, as well as to enable them 

 to acquire fit corporal traits, as is beautifully illustrated 

 by the differences in the sports of kittens and puppies. 

 We constantly meet passages in the writings of various 

 authors, wherein they attribute this or that mental 

 chansre in lower animals or meu to *' centuries of 

 domestication," or ''centuries of civilization," or "to 

 centuries " of this or that change in the environment, 

 the implication being that acquired mental traits are 

 transmitted and acciunulated, for otherwise the word 

 " century " would not be applied to creatures whose 

 lives are much shorter. The evidence, however, is over- 

 whelmingly against such a supposition. Our various 

 breeds of house dogs, for example, have all lived and 

 evolved under much the same conditions, and therefore 

 if acquired mental traits are transmissible, should ex- 

 hibit similar qualities. The difference between the dis- 

 positions of bulldogs and lapdogs, for instance, can only 

 have arisen (1) through artificial selection, or (2) through 

 differences in individually acquired (and not trans- 

 missible) traits; the latter being secondary to physical 

 conformation, which in the bulldog must tend, through 

 success in conflict, to produce a bold, resolute, and 

 confident spirit, and ia the lapdog a spirit much the 

 reverse. And here I may remark, that in all animals 

 capable of acquiring mental traits, the character of these 

 traits must in every case be profoundly influenced by 

 the physical conformation. A priori, very many of the 

 traits exhibited by domesticated animals must be ac- 

 quired, not inborn, since they are mentally so malleable 

 as to be capable of domestication, of adapting themselves 

 to an "abnormal" environment; a ijosteriori, these traits 

 are proved to be acquired and non-inheritable, since 

 every one of our domesticated animals, — dogs, cats, 

 horses, sheep, goats, pigs, poultry, &c., — when relieved of 



