THE STANDPOINT OF BIOLOGISTS. 33 



artificially induce the acquisition of some character, 

 and notice whether this is transmitted ; if it is not, 

 then the general operation of this kind of trans- 

 mission is rendered very doubtful. 



Many Cases of Supposed Transmission to be explained 

 by Selection. 



It is upon these two lines that Galton and Weismann 

 worked, and we may now follow in rough outline the 

 evidence they adduced. Darwin had been able to ex- 

 plain, to universal satisfaction, the evolution of many 

 types and varieties, as a result of selection alone ; 

 though certain cases of the supposed inheritance of 

 use and disuse, and of acquired instincts, caused at 

 times doubts to arise in his mind. But Weismann 

 has questioned this inheritance, and has shown that 

 as Darwin himself sometimes believed these may 

 readily be explained by selection alone. The gradual 

 increase, generation after generation, in the size of a 

 useful limb or the perfection of a valuable organ of 

 sense may readily be explained by selection. The 

 fact that the limb or organ is of use to the race in 

 its struggle will determine the survival of those born 

 with these serviceable parts well-formed, arid these in 

 their turn will produce others as favourably or more 

 favourably constituted, from whom further selection 



can take place. We cannot shut our eyes to the 



c 



