HISTOEICAL SKETCH. xix 



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, these being the ' adaptations ' of 

 the natural theologian." The author apparently believes 

 that organisation progresses by sudden leaps, but that 

 the effects produced by the conditions of life are gradual. 

 He argues with much force on general grounds that 

 species are not immutable productions. But I cannot 

 see how the two supposed " impulses ,: account in a 

 scientific sense for the numerous and beautiful co- 

 adaptations which we see throughout nature ; I cannot 

 see that we thus gain any insight how, for instance, a 

 woodpecker has become adapted to its peculiar habits 

 of life. The work, from its powerful and brilliant style, 

 though displaying in the earlier editions little accurate 

 knowledge and a great want of scientific caution, imme- 

 diately had a very wide circulation. In my opinion it 

 has done excellent service in this country in calling 

 attention to the subject, in removing prejudice, and in 

 thus preparing the ground for the reception of analogous 

 views. 



In 1846 the veteran geologist M. J. d'Omalius 

 d'Halloy published in an excellent though short paper 

 (' Bulletins de l'Acad. Boy. Bruxelles,' torn. xiii. p. 581) 



