II THE PROGRESS OF SCIENCE 99 



former, aided by a marvellous power of clear expo- 

 sition, placed upon an irrefragable basis the truth 

 that natural causes are competent to account for 

 all events, which can be proved to have occurred, 

 in the course of the secular changes which have 

 taken place during the deposition of the stratified 

 rocks. The publication of " The Principles of Geo- 

 logy," in 1830, constituted an epoch in geological 

 science. But it also constituted an epoch in the 

 modern history of the doctrine of evolution, by 

 raising in the mind of every intelligent reader this 

 question : If natural causation is competent to ac- 

 count for the not-living part of our globe, why 

 should it not account for the living part ? 



By keeping this question before the public for 

 some thirty years, Lyell, though the keenest and 

 most formidable of the opponents of the transmu- 

 tation theory, as it was formulated by Lamarck, 

 was of the greatest possible service in facilitating 

 the reception of the sounder doctrines of a later 

 day. And, in like fashion, another vehement op- 

 ponent of the transmutation of species, the elder 

 Agassiz, was doomed to help the cause he hated. 

 Agassiz not only maintained the fact of the pro- 

 gressive advance in organisation of the inhabitants 

 of the earth at each successive geological epoch, 

 but he insisted upon the analogy of the steps of 

 this progression with those by which the embryo 

 advances to the adult condition, among the highest 

 forms of each group. In fact, in endeavouring to 



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