FACTS OF INHERITANCE 159 



There is no doubt that modifications are very 

 conunon, that they are of much individual import- 

 ance, that they may have an indirect influence 

 through the body on the offspring (especially in 

 the case of mammaUan mothers), that they may 

 have an indirect importance in evolution in several 

 ways, but the precise point at issue is this : Does 

 a structural change in a fart of the body, induced by 

 use or disuse, or by change in surroundings and 

 nurture generally, ever influence the germ-plasm in 

 the reproductive organs in such a specific or re- 

 presentative way that the offspring will therd)y 

 exhibit the same modification that the parent ac- 

 quired, or even a tendency towards it ? We do not 

 know of any clear case which would at present 

 warrant the assertion that a somatic modification 

 is ever transmitted from parent to offspring. 



In regard to this important question, let us try to 

 clear the ground by noting a few of the common 

 misunderstandings.^ 



I. How can there be progressive evolution if 

 acquired characters are not entailed ? By the 

 accumulation of germinal variations, such as those 

 which have separated the higher from the lower 

 races of mankind. Yet Herbert Spencer actually 

 said, " Either there has been inheritance of acquired 

 characters, or there has been no evolution." In 

 1796 the speed of the English trotter was a mile 

 in 2 mins. 37 sees. ; it is now a mile in 2 mins. 

 10 sees., or less; but that is the result of the 

 selection of inborn variations, not of the trans- 

 mission of acquired characters. 



II. Many facts in nature are readily interpretable 



1 See " Heredity," by J. Arthur Thomson, (Murray. London 

 1908.) 



