CRITICISMS ON " THE ORIGIN OF SPECIES " 183 



is perfect of its kind, and needs no further development. Should, 

 however, a variety be useful and even maintain itself, there is no 

 obvious reason why it should change any further. The whole con- 

 ception of the imperfection of organisms and the necessity of their 

 becoming perfected is plainly the weakest side of Darwin's Theory, 

 and a pis aller (Nothbehelf) because Darwin could think of no other 

 principle by which to explain the metamorphoses which, as I also 

 believe, have occurred." 



Here again we must venture to dissent completely from 

 Professor Kolliker's conception of Mr. Darwin's hypothesis. 

 It appears to us to be one of the many peculiar merits of 

 that hypothesis that it involves no belief in a necessary and 

 continual progress of organisms. 



Again, Mr. Darwin, if we read him aright, assumes no 

 special tendency of organisms to give rise to useful varieties, 

 and knows nothing of needs of development, or necessity 

 of perfection. What he says is, in substance : All organisms 

 vary. It is in the highest degree improbable that any given 

 variety should have exactly the same relations to sur- 

 rounding conditions as the parent stock. In that case it 

 is either better fitted (when the variation may be called 

 useful), or worse fitted, to cope with them. If better, it 

 will tend to supplant the parent stock ; if worse, it will 

 tend to be extinguished by the parent stock. 



If (as is hardly conceivable) the new variety is so per- 

 fectly adapted to the conditions that no improvement upon 

 it is possible, it will persist, because, though it does not 

 cease to vary, the varieties will be inferior to itself. 



If, as is more probable, the new variety is by no means 

 perfectly adapted to its conditions, but only fairly well 

 adapted to them, it will persist, so long as none of the 

 varieties which it throws off are better adapted than itself. 



On the other hand, as soon as it varies in a useful way, i.e. 

 when the variation is such as to adapt it more perfectly- to 

 its conditions, the fresh variety will tend to supplant the 

 former. 



So far from a gradual progress towards perfection forming 

 any necessary part of the Darwinian creed, it appears to 

 us that it is perfectly consistent with indefinite persistence 

 in one estate, or with a gradual retrogression. Suppose, 

 for example, a return of the glacial epoch and a spread 

 of polar climatal conditions over the whole globe. The 

 operation of natural selection under these circumstances 

 would tend, on the whole, to the weeding out of the higher 



