28 Natural Selection and Amplimiixis 



propositions led up. In order to see more 

 clearly the issue raised, we may begin by 

 comparing our imaginary immortal with some 

 mortal double, who has reached the same level 

 of biological development within a few short 

 years. The bodies of both are related to 

 the simplest form of life — the one directly 

 the other indirectly — the one having de- 

 veloped from such a form by continuous 

 interaction with its environment, the other, 

 according to Weismann, having developed 

 from a continuous stock of germ-plasm, 

 entirely cut off from the environment since 

 the unicellular stage. Now in both cases 

 there is an "immortal" concerned — our im- 

 aginary individual in the one case, and 

 Weismann's hypothetical germ-plasm in the 

 other. Also the result attained is in both 

 cases the same ; and certainly it is the most 

 wonderful instance we know of what we call 

 an end, a Ti\Q%. The fundamental factors in 



