BOTANICAL SUBJECTS. 47 



IV.— NATURAL SELECTION. 



" It has been very often maintained that natural selection can 

 produce nothing new, but can only bring to the front something 

 which existed previously to the exercise of choice ; but this 

 argument is only true in a very limite^l 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, no 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 develop them, but 

 only as possibilities and not of necessity ; nor were they pre- 

 formed 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, 

 &c., not suddenly or discontiuuously, but working by the smallest 

 stages upon the variations that appear. These changes or varia- 

 tions must be looked upon as very insignificant, and are as I have 

 of late attempted to show* 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 

 * new ' organs, instincts, &c. 



" These processes may be compared to a man on a journey 

 who proceeds 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 



♦ Essay on Heredity. 



