THE CYCLE OF LIFE 409 



as safety-valves for overflowing energy, partly as the 

 muscular correlates of emotion, partly as opportunities 

 for the emergence of variations before too rigorous selection 

 begins, but mainly as periods for educating powers which 

 are essential in after-life. Animals, Groos says, do not 

 simply play because they are young ; they continue young 

 in order that they may play. For play is the young form 

 of work, and the animals who played best when young, 

 worked best, lived best, perhaps loved best, when they 

 grew up '. 



In his Childhood of Animals Dr. Chalmers Mitchell has 

 worked out the important thesis that the purpose of youth 

 is to give time for the breaking down of rigid instincts, and 

 their replacement by actions controlled by experience and 

 memory, by remembered results of experiment. We would 

 suggest that youth is the time when co-ordinations are 

 established between the instinctive processes of the lower 

 brain-centres and the intelligent processes of the cerebral 

 cortex. 



It is plain that youth is a perilous time ; why should there 

 be this tendency to lengthen it out ? The answer is that 

 it is the time for self-expression. The number of brain-cells 

 does not increase, but their interlinkings are complexified, 

 which means a growth of intelligence and a deepening of 

 feeling. Thus has youth been justified in the past ; so it is 

 justified every day. 



If Natural History is asked to give hints to the human 

 educationist and stranger things have happened one of 

 them will be this, as Chalmers Mitchell puts it : 



' Youth should be spent in blunting [a term apt to be 

 misunderstood ?] every instinct, in awakening and stimu- 

 lating every curiosity, in the gayest roving, in the wildest 



