i. 5 INFLUENCE OF ENVIRONMENT 7 



occasions, with our imperfect language, but it is a feeble descriptive 

 technique. I do not believe that it is satisfactory for biology and 

 especially not for zoology. By the life of an animal we mean all those 

 activities that make a certain pattern and serve to maintain that 

 pattern. In so far as we can describe this as a whole it is by comparing 

 it with other self-maintaining systems and particularly with those 

 self-controlling machines that we have made for ourselves. Biology 

 today has a great opportunity to explore the means by which animals 

 remain alive, using many sorts of descriptive technique, chemical, 

 electrical and, not least, the means by which mathematicians and 

 engineers describe whole complicated self-maintaining systems. It 

 is in such language that a fuller and richer account of living things 

 can be given. It is curious that objections to the use of scientific 

 terminology often claim that it somehow 'reduces' or 'restricts' our 

 view of life. Exactly the reverse is the case. Explaining human or 

 animal life in terms of 'spirits', good or bad, is only describing them 

 by comparison with themselves. Scientific description allows us to 

 break out of our narrow prison and to show how each of the many 

 aspects of life can be measured and compared with the forces that can 

 be detected throughout the universe. 



5. The influence of environment on life 



Growth is the addition of material to that which is already organized 

 into a living pattern. But the pattern is not fixed and invariate, even 

 throughout any one life. Each individual changes through its lifetime, 

 develops, as we say, and moreover is modified by the action upon it 

 of its surroundings. Those parts that are exercised by the interaction 

 of the animal's tendencies and the surrounding circumstances increase 

 in amount (hypertrophy), while any disused parts undergo atrophy or 

 reduction. The pattern is thus able to conform to a considerable 

 extent to the exigencies of change in the external world. It could be 

 imagined that a sufficiently plastic animal organization would be able 

 in this way, if its tendencies to survival were strong enough, to mould 

 itself to all the changes of climate through the millennia, so that a 

 great variety of animal tvpes would arise by use and disuse alone. 

 Only a limited degree of change is possible in this way, however, and 

 it is not such changes either of development or by the direct influence 

 of environment that we call 'evolution'. There is abundant evidence 

 that the result of such interaction between organism and environment 

 is not handed on in the genetic code. Acquired characters are not 

 inherited. 



