Chap. II.] VARIATION UNDER NATURE. 51 



CHAPTER II. 



VAEIATION UNDER NATTTEB. 



Variabilit J-— Individual diflEerenoes— Doubtful species— Wide rang- 

 ing, much diffused, and common species, vary most— Species of 

 tb^ larger genera in each country vary more frequently than 

 the species of the smaller genera— Many of the species of the 

 la ger genera resemble varieties in being very closely, but un- 

 eqially, related to each other, and in having restricted ranges. 



Be/okb applying the principles arrived at in the last 

 chapter .to organic beings in a state of nature, we must 

 briefly ciscuss whether these latter are subject to any 

 variation. To treat this subject properly, a long 

 catalogue' of dry facts ought to be given; but these 

 I shall TL^^erve for a future work. Nor shall I here 

 discuss the various definitions which have been given 

 of the term species. No one definition has satisfied all 

 naturalists; yet every naturalist knows vaguely what 

 he means when he speaks of a species. Generally the 

 term includes the unknown element of a distinct act of 

 creation. The term "variety" is almost equally 

 difficult to define; but here community of descent 

 is almost universally implied, though it can rarely be 

 proved. We have also what are called monstrosities; 

 but they graduate into varieties. By a monstrosity I 

 presume is meant some considerable deviation of 

 structure, generally injurious, or not useful to the 

 species. Some authors use the term " variation " in a 



