20 A Century of Science 



lution, especially the law that organs and faculties 

 tend to increase with exercise, and to dimmish with 

 disuse. His weakest point was the disposition to 

 imagine some inherent and ubiquitous tendency to- 

 ward evolution, whereas a closer study of nature has 

 taught us that evolution occurs only where there 

 is a concurrence of favourable conditions. Among 

 others who maintained some theory of evolution 

 were the two Geoffrey Saint-Hilaires, father and 

 son, and the two great botanists, Naudin in France 

 and Hooker in England. In 1852 the case of evo- 

 lution as against special creations was argued by 

 Herbert Spencer with convincing force, and in 

 1855 appeared " The Principles of Psychology," 

 by the same author, a book which is from begin- 

 ning to end an elaborate illustration of the process 

 of evolution, and is divided from everything that 

 came before it by a gulf as wide as that which 

 divides the Copernican astronomy from the Ptole- 

 maic. 



The followers of Cuvier regarded the methods 

 and results of these evolutionists with strong dis- 

 approval. In the excess of such a feeling, they 

 even went so far as to condemn all philosophic 

 thinking on subjects within the scope of natural 

 history as visionary and unscientific. Why seek 

 for any especial significance in the fact that every 



