LIFE AND DEATH. 137 



the exercise of choice ; but this argument is only true in a very 

 limited sense. The complex world of plants and animals which we 

 see around us contains much that we should call new in comparison 

 with the primitive beings from which, as we believe, everything 

 has developed by means of natural selection. No leaves or flowers, 

 no digestive system, no lungs, legs, wings, bones or muscles were 

 present in the primitive forms, and all these must have arisen 

 from them according to the principle of natural selection. These 

 primitive forms were in a certain sense predestined to develope 

 them, but only as possibilities, and not of necessity ; nor were they 

 preformed in them. The course of development, as it actually took 

 place, first became a necessity by the action of natural selection, 

 that is by the choice of various possibilities, according to their 

 usefulness in fitting the organism for its external conditions of life. 

 If we once accept the principle of natural selection, then we must 

 admit that it really can create new structures, instincts, etc., not 

 suddenly or discontinuously, but working by the smallest stages 

 upon the variations that appear. These changes or variations must 

 be looked upon as very insignificant, and are, as I have of late 

 attempted to show 1 , quantitative in their nature ; and it is only 

 by their accumulation that changes arise which are sufficiently 

 striking to attract our attention, so that we call them c new ' 

 organs, instincts, etc. 



These processes may be compared to a man on a journey who pro- 

 ceeds from a certain point on foot by short stages, at any given time, 

 and in any direction. He has then the choice of an infinite number 

 of routes over the whole earth. If such a man begins his wanderings 

 in obedience to the impulse of his own will, his own pleasure or 

 interest, proceeding forwards, to the right or left, or even back- 

 wards, with longer or shorter pauses, and starting at any particular 

 time, it is obvious that the route taken lies in the man himself and 

 is determined by his own peculiar temperament. His judgment, 

 experience, and inclination will influence his course at each turn 

 of his journey, as new circumstances arise. He will turn aside 

 from a mountain which he considers too lofty to be climbed ; he 

 will incline to the right, if this direction appears to afford a better 

 passage over a swollen stream ; he will rest when he reaches 

 a pleasant halting- place, and will hurry on when he knows that 

 1 See the preceding essay ' On Heredity.' 



