CH. XIV] GENERAL DISCUSSION 187 



ultimately become the parent, not only of many species, but of a 

 group of generic offspring forming a sub-tribe or larger division. 

 The whole family will at last end in the tail of genera containing 

 one species each, as shown in the hollow curve. The oldest genera 

 will have the most species, and the number will diminish as does 

 the age, till we come to the tail of monospecific genera. 



There is thus very strong evidence to the effect that evolution 

 has gone on without any direct reference to natural selection so 

 far as we can at present see. The new form will appear, whether 

 it be desirable, or suitable, or not, and whether it then survive 

 will depend upon the action of natural selection, with reference 

 to the conditions at the moment. The business of natural selec- 

 tion is (1) to kill out everything in any way unsuitable to the 

 conditions that surround it at the time, either at its first ap- 

 pearance upon the scene, or when a change of conditions occurs ; 

 and (2) to adjust to its surroundings, if possible, every new form 

 that comes into the place, whether a new species just born, or a 

 species newly arrived from somewhere else. There is thus plenty 

 of occupation left for natural selection, and in a field where its 

 usefulness and value have never been questioned. The early 

 pioneer species will, of course, get the best chance, and as each 

 newcomer arrives, increasingly close and careful adjustment will 

 be needed, adjustment which natural selection will apply without 

 fear or favour. 



Lastly, the evidence is equally strong that in the process of 

 evolution, at any rate as a general rule, the new species formed 

 (which might also be a new genus or even new family if the muta- 

 tion were a little larger) would appear at one step by sudden 

 mutation. Evolution goes on, but we can see no reason at present 

 that will determine that it shall go in any particular direction, 

 especially in one that shows greater adaptation. The mere fact of 

 the survival of the "lower" forms in such numbers, like mosses, 

 ferns, and liverworts, is against the idea, of any rapid progress in 

 adaptation, but probably when an "adaptation" appears, such 

 for example as climbing habit, it will be allowed or encouraged to 

 survive, though why it should appear is at present a mystery. 



It is an inspiring thought that so great and complex a process 

 as evolution must have been has not been a mere matter of 

 chance, but has behind it what one may look upon as a great 

 thought or principle that has resulted in its moving as an ordered 

 whole, and working itself out upon a definite plan, as other 

 branches of science have already been shown to do. Darwinism 

 made the biological world a matter of chance. Differentiation, 



