PT. II, CH. XX] THE ORIGIN OF SPECIES 205 



and my present object is not to add to it, but to criticise certain 

 aspects of the theory, and to show in what directions it has 

 failed to give us satisfactory explanations of phenomena, or 

 fruitful subsidiary hypotheses upon which to work. To suggest 

 a doubt of its enormous value in the advance of knowledge would 

 be to rank all the workers of the last sixty years as upon the 

 intellectual level of the Bushman or the Esquimaux. 



There can be little doubt, however, that during recent years 

 the theory of natural selection has become what we may call a 

 limiting factor in the progress of biology, and the time seems to 

 me to have arrived when we ought to consider the advice given 

 by Sir Joseph Hooker soon after his first acceptance of the 

 theory : 



"The advocate of creation by variation may have to stretch 

 his imagination to account for such gaps in a homogeneous 

 system as will resolve its members into genera, classes, and 

 orders, but in doing so he is only expanding the principle which 

 both theorists {i.e. special creationists and natural selectionists) 

 allow to have operated in the resolution of some groups of indi- 

 viduals into varieties:... Natural Selection explains things better 

 ...it is to this latter that the naturalist should look... holding 

 himself ready to lay it down when it shall prove as useless for 

 the further advance of science, as the long serviceable theory of 

 special creations, founded on genetic resemblances, now appears 

 to me to be." 



Went (112, p. 270) has said that we ought to drop all teleo- 

 logical explanations, and not consider nature as having any aim. 

 This may seem somewhat drastic, but as yet we are without 

 any e^•idence as to Avhat is the aim of nature, though the work 

 that has been described above seems to show that she perhaps 

 has one, for it seems evident that the evolutionary clock was 

 wound up to run on a very definite plan. But for what nature 

 is aiming in this definite way, we are completely ignorant, and 

 it will, it seems to me, prove more wise, in the present state of 

 science, to follow Went's advice, leaving out of serious account 

 as yet any suppositions as to the ultimate aim of nature. 



We have shown in the preceding chapters that the phenomena 

 of distribution, whether it be distribution in space of species 

 and genera, or distribution in time, as exhibited by the grouping 

 of species into genera of various sizes, can be graphically repre- 

 sented by hollow curves, which could if required be produced 

 in tens of thousands. It is clear that such a general phenomenon 

 must have a general explanation, and that this must be largely 



