THE PERIOD OF INCUBATION 71 



the providence of God, the results, first, of an impulse 

 which has been imparted to the forms of life, advancing 

 them, in definite times, by generation, through grades 

 of organisation, terminating in the highest dicotyledons 

 and vertebrata, these grades being few in number, and 

 generally marked by intervals of organic character, 

 which we find to be a practical difficulty in ascertaining 

 affinities; second, of another impulse connected with 

 the vital forces, tending, in the course of generations, to 

 modify organic structures in accordance with external 

 circumstances, as food, the nature of the habitat, and 

 the meteoric agencies/ Now it is clear at once that 

 these two supposed ' impulses ' are really quite miracu- 

 lous in their essence. They do not help us at all to a 

 distinct physical and realisable conception of any natural 

 agency whereby species became differentiated one from 

 the other. They lay the whole burden of species- 

 making upon a single primordial supernatural impetus, 

 imparted to the first living germ by the will of the 

 Creator, and acting ever since continuously it is true, 

 but none the less miraculously for all that. For many 

 creations Chambers substitutes one single long creative 

 nisus : where Darwin saw natural selection, his Scotch 

 predecessor saw a deus ex machina, helping on the 

 course of organic development by a constant but unseen 

 interference from above. He supposed evolution to be 

 predetermined by some intrinsic and externally im- 

 planted proclivity. In short, Chambers's theory is 

 Lamarck's theologised, and spoilt in the process. 



The book had nevertheless a most prodigious and 

 perfectly unprecedented success. The secret of its 

 authorship was keenly debated and jealously kept. The 



