982 LIFE : OUTLINES OF GENERAL BIOLOGY 



Heredity, the past living on in the present, is the first Factor, and 

 the greatest of the three. 



The second Factor is Environment — all manner of surrounding 

 influences that play upon the living creature, making deep dints 

 or giving light touches, awakening some buds and frost-biting others, 

 encouraging and depressing, training and thwarting. Environment is 

 the second factor, and some of us think that it comes a better second 

 than others of us will allow. 



The third Factor is Function— whsi the creature does or does not 

 do, the influence of use and disuse, or work and play, of exercise 

 and rest. When we consult a book like Arlidge's Diseases of Occupa- 

 tions — a grim curiosity for future ages — ^we realise what an important 

 factor function may be for evil as well as good in the individual life. 

 The importance of function as a life-shaping factor is expressed in 

 various wise sayings : "By force of forging one becomes a forgesmith." 

 "What you have inherited from your ancestors you must use if it 

 is to be your very own." In the language of the immortal parable, 

 we must trade with our talents. 



Before giving illustrations of the three great factors, one may be 

 tempted to ask if there are not four. A swallow born and bred in 

 Britain flies south at the end of summer, and the Aberdeen University 

 Bird Migration Inquiry has helped to prove that such a swallow may 

 return the following spring to the very farm-steading, and nest, 

 of its birth and youth — a wonderful homing. That it can make the 

 double journey successfully depends mainly on its inheritance, but 

 partly on its functioning, its early training in flight, and partly on 

 environment, as from the nutrition which gives it strength to fly 

 to the stimuli which pull the trigger of the migratory instinct. But 

 is there not also a cosmic factor — of old called Fate, by some called 

 Chance, or, again, Nature or Circumstance, quite uncontrollable by 

 the creature itself and careless of it, which offers or withholds 

 opportunities, which meets some migrants with a fatal storm and 

 offers others a fair haven? Is not one of the factors in our own 

 life a giving or withholding of opportunities which we, at any 

 rate, have nothing to do with, which we call providence when 

 it is with us, and chance when it is against us? But, perhaps, 

 this may be included as part of our environment. Indiscriminate 

 Selection has to be recognised — as from earthquake to change of 

 weather. 



Estimate of Nurtural Influence. — ^The modern idea of the 

 biological controllability of life, surely dating from Darwin and 

 Pasteur, led, not unnaturally, to an indulgence in over-sanguine 

 hopes as to the ameliorative influences of function and environ- 

 ment. This was held to be demonstrable for the individual, and 

 before the days of Galton's and Weismann's wholesome scepticism 

 as to the transmission of bodily modifications or individually acquired 



