216 SPECULATIVE SCIENCE 



live, the weak die ; and so, generation after generation, nature?, 

 by a metaphor, may be said to choose certain animals, even as 

 man does when he desires to raise a special breed. The device 

 of nature is based on the attributes most useful to the animal ; 

 the device of man on the attributes useful to man, or admired 

 by him. All must agree that the process termed natural selec- 

 tion is in universal operation. The followers of Darwin believe 

 that by that process differences might be added, even as they 

 are added by man's selection, though more slowly, and that this 

 addition might in time be carried to so great an extent as to 

 produce every known species of animal from one or two pairs, 

 perhaps from organisms of the lowest known type. 



A very long time would be required to produce in this way 

 the great differences observed between existing beings. Geo- 

 logists say their science shows no ground for doubting that 

 the habitable world has existed for countless ages. Drift and 

 inundation, proceeding at the rate we now observe, would 

 require cycles of ages to distribute the materials of the surface 

 of the globe in their present form and order ; and they add, for 

 aught we know, countless ages of rest may at many places have 

 intervened between the ages of action. 



But if all beings are thus descended from a common ancestry, 

 a complete historical record would show an unbroken chain of 

 creatures, reaching from each one now known back to the first 

 type, with each link differing from its neighbour by no more 

 than the several offspring of a single pair of animals now differ. 

 We have no such record ; but geology can produce vestiges 

 which may be looked upon as a few out of the innumerable 

 links of the whole conceivable chain, and what, say the followers 

 of Darwin, is more certain than that the record of geology must 

 necessarily be imperfect? The records we have show a certain 

 family likeness between the beings living at each epoch, and 

 this is at least consistent with our views. 



There are minor arguments in favour of the Darwinian hypo- 

 thesis, but the main course of the argument has, we hope, been 

 fairly stated. It bases large conclusions as to what has hap- 

 pened upon the observation of comparatively small facts now 

 to be seen. The cardinal facts are the production of varieties 

 by man, and the similarity of all existing animals. About the 



