J CALIFORNIA ACADEMY QF SCIENCES. 



materially affect the work of the second part, although 

 the theories concerning the special investigations in the 

 evolution of color in birds are largely founded upon the 

 principles laid down in Part I. Although this first part 

 is necessarily of a general character, nothing has been 

 inserted which has not some bearing upon the investiga- 

 tions which follow. An attempt has been made to dis- 

 cuss the general principles of evolution according to a 

 logical system, the subject of the inheritance of acquired 

 characters being treated first, as it is the most funda- 

 mental question in dispute. 



The doctrine of evolution is by no means modern in 

 its conception, having been dimly foreshadowed from 

 the days of Aristotle; but it was first suggested in a 

 plausible scientific form by Jean Lamarck, who, in 1809, 

 published his Philosopliie Zoologique. He attempted 

 to account for the changes in organic forms almost ex- 

 clusively by the principles of the use and disuse of parts 

 of which doctrine he was the originator. His views were 

 hardly noticed at the time they were announced, but a 

 little later Geoffrey St. Hilaire was more successful in 

 calling the attention of the scientific world to his own 

 closely related theory of the action of the environment 

 in producing the changes in organic beings; although 

 his views were not generally accepted by the naturalists 

 of the day The nature and extent of his theory is ex- 

 plained in the following Avords of Haeckel.* " He con- 

 ceives the organism as passive, in regard to the vital 

 conditions of the outer world, while Lamarck, on the 

 contrary, regards it as active. Geoffroy thinks, for ex- 

 ample, that birds originated from lizard-like reptiles, 

 simply by a diminution of the carbonic acid in the at- 

 mosphere, in consequence of which the breathing pro- 



•"Historj' of Creation, I., p. 117. 



