FROM LAMARCK TO ST. HILAIRE 245 



Lamarck foresaw the great difficulties which 

 would arise in classification from his theory of 

 the filiation and mutability of all animal and 

 plant types, and he fully grasped the immediate 

 bearings of his theory upon the definition of spe- 

 cies. He v/rites: "Nature exhibits to us indi- 

 viduals succeeding each other, but the species 

 among them have only a relative stability, and 

 are only temporarily invariable." Quatrefages 

 remarks that he does not clearly distinguish be- 

 tween species, races, and varieties. 



The definition of species was in Lamarck's 

 time the test of the creed of the naturalist. Isi- 

 dore St. Hilaire, in the Histoire Naturelle Ge- 

 nerale,^ gives us an interesting outline of the his- 

 tory of these definitions, beginning with that of 

 Linna?us, including Buffon's earlier and later 

 definitions and Cuvier's later definitions; La- 

 marck's is admirable: 



A species is a collection of similar individuals 

 which are perpetuated by generation in the same con- 

 dition as long as their environment does not change 

 sufficiently to bring about variation in their habits, 

 their character, and their form. 



Certainly no better definition of a species could 

 be given today. 



We have seen that Lamarck's final conception 



III, 1869, p. 410. 



