XL] EVOLUTION IN BIOLOGY. 297 



du Globe " were held to be models of sound scientific 

 thinking, while the really much more sober and 

 philosophical hypotheses of the " Hydrogeologie " were 

 scouted. For many years it was the fashion to speak 

 of Lamarck with ridicule, while Treviranus was 

 altogether ignored. 



Nevertheless, the work had been done. The con- 

 ception of evolution was henceforward irrepressible, 

 and it incessantly reappears, in one shape or another, 1 

 up to the year 1858, when Mr. Darwin and Mr. 

 Wallace published their " Theory of Natural Selection." 

 The " Origin of Species " appeared in 1859 ; and it is 

 within the knowledge of all whose memories go back 

 to that time, that, henceforward, the doctrine of evolu- 

 tion has assumed a position and acquired an import- 

 ance which it never before possessed. In the " Origin 

 of Species," and in his other numerous and important 

 contributions to the solution of the problem of bio- 

 logical evolution, Mr. Darwin confines himself to the 

 discussion of the causes which have brought about the 

 present condition of living matter, assuming such 

 matter to have once come into existence. On the 

 other hand, Mr. Spencer 2 and Professor Haeckel 3 

 have dealt with the whole problem of evolution. The 

 profound and vigorous writings of Mr. Spencer em- 

 body the spirit of Descartes in the knowledge of our 

 own day, and may be regarded as the " Principes de la 



1 See the " Historical Sketch " prefixed to the last edition of the 

 " Origin of Species." 



2 "First Principles" and "Principles of Biology," 1860-1864. 



3 "Generelle Morphologic," 1866. 



