YOUNG THINGS 29 



common dog-whelk (Purpura lapillus), which are fastened 

 to the shelves among the rocks. The numerous eggs in 

 each capsule or vase are not all hatched at the same time ; 

 some are a little earlier than the others, and the pioneers 

 devour the laggards as they come on the scene a curious 

 instance of cannibalism in the cradle, an extreme form of 

 the struggle for existence at the very threshold of life. 



One of the biological certainties in regard to young 

 things is their extraordinary plasticity, their power of 

 acquiring modifications as the results of some peculiarity 

 in nurture. By modifications we mean structural changes 

 induced by peculiarities in surroundings or functioning. 

 Every inheritance implies an appropriate environment of 

 nutritive and other stimuli, apart from which the legacy 

 cannot be realised. The inherited nature requires its 

 appropriate nurture, and peculiarities in nurture whether 

 of food or sunshine, of use or disuse, of education or the 

 lack of it result in modifications. We must return to 

 this very important subject, but meanwhile we note one 

 of the general impressions of the Spring season, that young 

 things are plastic, much in the grip of their surroundings, 

 and very liable both for good and ill to put on veneer, to 

 acquire modifications which are neither inherited nor 

 transmissible. 



The tricks that one can play with tadpoles, cater- 

 pillars, and other young things are endless ; and the extra- 

 ordinary modifiability of young children is one of the great 

 facts of life. Every one knows and feels this in a general 

 way ; poets like Walt Whitman and Matthew Arnold have 

 given it fine expression, but perhaps only the biologists 

 quite realise the plasticity of the young life. It is, within 

 limits, like clay in the potter's hands. This is the other 

 side of heredity, so to speak. 



Another general biological impression that we get from 



