THE PLASTICITY OF LIFE 199 



materials for further progress, or it may be, of course, 

 degeneracy. 



When we realise how strong racial inertia is, and how 

 literally we are chips of that old block which is the average 

 of our stock, when we recognise that our inheritance is a 

 mosaic of ancestral contributions, when we learn the 

 inexorableness of what is called filial regression, which 

 brings the children of unusually gifted or unusually ungif ted 

 parents towards the mean of the race, we are apt to become 

 fatalistic. Therefore it is useful to illustrate, especially 

 in the Spring, something of the other aspect of life its 

 plasticity. It must have been with some good reason that 

 a sagacious thinker like Buckle depreciated the importance 

 of heredity ; the reason was his vivid impression of the 

 power of nurture surroundings and habits in moulding 

 character, both bodily and mental. 



There is a well-known shore animal, Lingula by name, 

 one of the lamp-shells or Brachiopods, which has been living 

 in the world since the earliest ages (the Cambrian) of 

 which we have fossil remains. Its direct ancestry is trace- 

 able for millions, probably several hundreds of millions, of 

 years. It is literally a " living fossil." It flourished in 

 the Cambrian ages, and flourishes very well still. It is 

 so abundant to-day on some shores that its body is sold 

 by the peck for food. Now the point of particular interest 

 is, that this ultra-conservative animal has not changed all 

 the time so far as we can tell from examination of the 

 shell. There may have been internal changes in the soft 

 parts, or there may not ; we have no evidence. But as 

 regards externals, Lingula has lived on for millions of 

 years unchanged. It illustrates a remarkable hereditary 

 constancy, sustained throughout a lapse of time which is 

 so great that we cannot even vaguely imagine it. It is 

 obvious that if all the living creatures we know had a story 



