CHAPTER XVII 



THE " PHILOSOPHIE ZOOLOGIQUE " 



Lamarck's mature views on the theory of descent 

 comprise a portion of his celebrated Philosophie zoo- 

 logique. We will let him tell the story of creation by 

 natural causes so far as possible in his own words. 



In the avertissement , or preface, he says that his 

 experience has led him to realize that a body of pre- 

 cepts and of principles relating to the study of 

 animals and even applicable to other parts of the 

 natural sciences would now be useful, our knowledge 

 of zoological facts having, for about thirty years, made 

 considerable progress. 



After referring to the differences in structure and 

 faculties characterizing animals of different groups, 

 he proceeds to outline his theory, and begins by 

 asking : 



" How, indeed, can I consider the singular modifi- 

 cation in the structure of animals, as we glance over 

 the series from the most perfect to the least perfect, 

 without asking how we can account for a fact so 

 positive and so remarkable — a fact attested to me by 

 so many proofs ? Should I not think that nature has 

 successively produced the different living beings by 

 proceeding from the most simple to the most com- 

 pound ; because in ascending the animal scale from 

 the most imperfect up to the most perfect, the organi- 



