&TIENNE AND ISIDORE GEOFFROY. 327 



change of habits in the creature, he is almost weari- 

 some in his insistence on the fact that the habit will 

 not change, unless the conditions of life also do so. 

 With both writers then it is change in the relative 

 positions of the exterior circumstances, and of the 

 organism, which results in variation, and finally in 

 specific modification. 



Here is another sketch of tienne Geoffroy, also by 

 his son Isidore. 



In 1795, while Lamarck was still a believer in immu- 

 tability, Etienne Geoffroy St. Hilaire " had ventured 

 to say that species might well be ' degenerations 

 from a single type,' " but, though he never lost sight 

 of the question, he waited more than a quarter of a 

 century before passing from meditation to action. " He 

 at length put forward his opinion in 1825, he returned 

 to it, but still briefly, in 1828 and 1829, and did not 

 set himself to develop and establish it till the year 

 1831 the year following the memorable discussion 

 in the Academy, on the unity of organic composi- 

 tion."* 



"If," says his son, "he began by paying homage 

 to his illustrious precursor, and by laying it down as 

 a general axiom, that there is no such thing as fixity 

 in nature, and especially in animated nature, he follows 

 (his adhesion to the general doctrine of variability by a 

 dissent which goes to the very heart of the matter. 

 And this dissent becomes deeper and deeper in his 

 later works. Not only is Geoffroy St. Hilaire at pains 

 to deny the unlimited extension of variability which 

 * 'Hist. Nat. Gen.,' torn. ii. 413. 



