THE SUCCESSION OF ANIMAL FORMS 197 



what extent they can be known by us, and to what extent they 

 may include processes of derivation, it is impossible now to 

 say. At present we must recognise in the prevailing theories 

 on the subject merely the natural tendency of the human mind 

 to grasp the whole mass of the unknown under some grand 

 general hypothesis, which, though perhaps little else than a 

 figure of speech, satisfies for the moment. We are dealing 

 with the origin of species precisely as the alchemists did with 

 chemistry, and as the Plutonists and Neptunists did with 

 geology ; but the hypotheses of to-day may be the parents of 

 investigations which will become real science to-morrow. In 

 the meantime it is safe to affirm that whatever amount of truth 

 there may be in the several hypotheses which have engaged 

 our attention, there is a creative force above and beyond them, 

 and to the threshold of which we shall inevitably be brought, 

 after all their capabilities have been exhausted by rigid in- 

 vestigation of facts. It is also consolatory to know that 

 species, in so far as the Modern period, or any one past geo- 

 logical period may be concerned, are so fixed that for all 

 practical purposes they may be regarded as unchanging. They 

 are to us what the planets in their orbits are to the astronomer, 

 and speculations as to the origin of species are merely our 

 nebular hypotheses as to the possible origin of worlds and 

 systems. 



REFERENCES : Address as Vice-President of American Association at 

 Detroit, 1875. "The Chain of Life in Geological Time," London, 

 1879. Addresses to Natural History Society of Montreal, published 

 in Canadian Naturalist, "Apparition of Animal Forms," Princeton 



