I30 



FOOT-NOTES TO EVOLUTION. 



Lamarck's much-discussed " fourth law " of develop- 

 ment reads as follows: "All that has been acquired, 

 begun, or changed in the structure of the 

 Inheritance of individuals in their lifetime is preserved 



acquired charac- . j ..• j ^ -4... ^ ^ ..u 



m reproduction and transmitted to the 



ters. '^ . ^ , 



new individuals which spring from those 



who have inherited the change." 



" Change of function produces change of structure," 

 so Herbert Spencer tells us ; " it is a tenable hypothesis 

 that changes of structure thus produced are inheritable." 



But though this may be a tenable hypothesis, the 

 opposite hypothesis has not been clearly shown to be 

 intenable. It seems to be true that any great physical 

 weakness on the part of Richard Roe's parents would 

 tend to lower his constitutional vigour, whatever the 

 origin of such weakness might be. If so, such weakness 

 might appear as a large deficiency in his power of using 

 his equipment. It may be, too, that any extreme degree 

 of training, as in music or mathematics, might determine 

 in the offspring the line of least resistance for the move- 

 ment of his faculties. Perhaps Richard Roe would find 



force on the generation that develops them. Acquired characters 

 are never inherited. Other investigators, equally wise, Herbert 

 Spencer and Lester F. Ward, for example, do not admit that any 

 gain or loss to the individual is without its effect on succeeding 

 generations, and thus on the species. X and Y are inherited just 

 as B or B' may be. 



Let us assume that they are inherited in some degree, and let us 



^ I j^' Y Y' 



represent this inheritance of acquired characters as pr " 



The divisor Q reducing all acquired characters of the parent is an 

 unknown quantity of large and perhaps variable value. If large, 

 the value of the fraction will be correspondingly small. In Weis- 



X Y 



mann's view, Q should equal infinity, in which case -^ or pr would 



be nothing at all. This would be the symbol of non-inheritance. 



