3&i IN StARRY REALMS. 



but enough has been said to show that in the great prin- 

 ciple of natural selection we have a means of producing 

 animals and plants which in the course of time will differ 

 widely from other organisms from the same progenitors. 



No one has ever seen a new species developed by 

 natural selection; but this is because no one has ever 

 lived long enough for that purpose. The circumstantial 

 evidence in favour of natural selection is indeed so strong 

 that no unprejudiced person can refuse to accept it. That 

 evidence has of late years been poured out with a pro- 

 fusion which could hardly have been anticipated at the 

 time when the " Origin of Species " was published. En- 

 tombed within solid rocks we find fossil remains of the 

 former inhabitants of our earth. There lies in these rocks 

 a record of vast extent and of the utmost interest ; but 

 that record is to a great extent screened from our view. 

 Here and there fossils have been brought to light ; but 

 the greater part of the earth has never been examined, 

 and we have as yet only the veriest fragments of the 

 geological record before us. But these fragments of the 

 record are of great importance ; they show us several 

 of the links which connect one class of animals with 

 another in the way the Darwinian theory suggests ; and 

 they encourage us to hope that, when the geological 

 record shall have been fully explored, we shall have 

 glimpses of a majestic panorama of the salient points in 

 the history of life on our globe. 



Mathematicians are long accustomed to the use of what 

 is known as the infinitesimal calculus. It is indeed 

 chiefly the infinitesimal calculus which has raised the 

 science of mathematics to its present position, and which has 



