ISIDORE ST. HILAIRE. 207 



of species ' (rather than of the mutabiHty) in his 

 classic work, Histoire Generale et Particultere 

 d' Anomalies de V Organization, 1832, and his 

 U Histoire Naturelle des Regnes Organigiies. He 

 was undoubtedly swayed by the difficulty of finding 

 positive evidence for transformation, and further 

 by the negative evidence of the stability of species 

 afforded by the rich collections of mummied animals 

 brought back from Egypt. Thus, in his theory, 

 he dwelt upon the limited variability rather than 

 the mutability of species, believing in transmission 

 only to the point of forming a new race. This is 

 fully set forth in his Histoire Naturelle (Vol. I., 

 p. 431). At the conclusion of his review of the 

 history of opinion upon Evolution in France, he 

 gives it, as his own opinion, that characters are 

 neither actually fixed nor variable, both depending 

 upon the fixity or the variability of environment. 

 New characters are the resultant of two forces : 

 first, the modifying influence of new surroundings ; 

 and, second, the conserving influence of Heredity. 

 When the former predominates, variations result, 

 such as are seen among savages and in the domes- 

 tication of animals. These variations among wild 

 animals extend to modifications of colour and exter- 

 nal characters, but in domestication the differences 

 are much more marked. So much for changes 

 going on at the present time. As to past time, the 

 ' theory of limited variability ' links itself with that 

 of ' filiation,' or descent from analogous forms, as 



