XVI ARE ACQUIRED CHARACTERS INHERITED ? 317 



question before the scientific world in a manner which 

 allows it to be fully discussed, tested, and controverted.^ 



This detailed theory is far too complex and technical to 

 be explained in a short chapter ; but as its truth implies 

 that the inheritance of acquired variations is not a law of 

 nature, and as Mr. Herbert Spencer has recently set forth 

 some fresh arguments in favour of such inheritance, 

 and has also reinforced some of his former arguments (in 

 two articles in the Contemporary Beviev;), while an Ameri- 

 can naturalist has just issued a work,"^ in the introduction 

 to which he discusses the same question, and summarises 

 what seem to him the strongest arguments that have 

 been advanced on both sides, concluding also in favour of 

 the inheritance of such characters — a good opportunity is 

 offered to review this evidence, and to show, as the present 

 writer thinks he can show, that all the alleged facts and 

 arguments are inconclusive, and that the balance of the 

 evidence yet adduced is altogether in favour of such char- 

 acters not being inherited. 



What are Acquired Characters ? 



It is first necessary to understand clearly what is meant 

 by " acquired characters," as even naturalists occasionally 

 miss the essential point, and take any peculiarit}^ that 

 appears in an individual during life to be an " acquired 

 character." But such peculiarities are usually inherited 

 from some ancestor, unless they can be clearly traced to 

 some special conditions to which the individual's body 

 has been exposed. As an illustration, let us suppose twin 

 brothers, very similar in all physical and mental characters, 

 to be subject during life to very different influences : one 

 being brought up from childhood to city life and kept 

 closely at a desk till middle age, the other living always 

 in the country and becoming a working farmer. If the 



^ The Germ Plasm: a Theory oj Heredity, by August Weismann. 

 Walter Scott. London, 1893. 



- Evolution of the Colours of North- American Land Birds, hy Charles 

 A. Keeler, California Academy of Sciences, San Francisco, January 

 1893. 



