CHAP, xvm A "FAIRY TALE OF SCIENCE"? 245 



root could not be healthy ; yet plant is never derived 

 from plant, and still less is root derived from plant ; 

 every root is derived from root ; every plant is derived 

 from root. Another image we might use is that of 

 a river like the Nile, flowing through countries which 

 can yield it no tributaries. The great river flows 

 majestically on, essentially the same as it was many 

 hundreds of miles up channel; imparting life wher- 

 ever it goes, but receiving nothing. Such a river of 

 life is "germ plasm," flowing through the genera- 

 tions, yielding to all of them support, but never 

 affected by them. 



There is, however, a difference which our images 

 fail to bring out. On Weismann's view, evolutionary 

 change is always at work, acting through natural 

 selection. Permutations and combinations are always 

 being remodelled let us say, combinations of play- 

 ing cards. The cards were originally dealt at the 

 dawn of animal and vegetable life ; and no fresh kind 

 of card has ever been introduced. Yet the " hands " 

 with which the game is played have, on the whole, 

 steadily improved from generation to generation, and 

 from age to age. How is that possible ? Because 

 these cards are alive. These cards multiply, aces 

 begetting aces, and kings begetting kings. Many 

 and many a hand has been torn up and flung away 

 in the process of natural selection; and accordingly 

 the surviving hands have become very strong all 

 court cards, or trumps, or powerful sequences. 1 



1 I do not know if Weismann means this ; but it seems to lie in the 

 theory. Efficient begets efficient, as surely as non-efficient begets non- 

 efficient. Quantities seem capable of indefinite improvement, though 

 the theory admits of no fresh ultimate quality. 



