VAEIATION UNDER NATURE. Chap. II. 



CHAPTER II. 



VARIATION UXDER NATURE. 



Variability— Individual Differences— Doubtful Species— Wide-ranging, much dif- 

 fused, and Common Species, vary meet- Species of the Larger Genera in each 

 Country vai"y more frequently than the Species of the Smaller Genera— Many of 

 the Species of the Larger Genera resemble Varieties in being very closely, bat 

 unequally, related to each other, and in having Restricted Ranges. 



Before applying the principles arrived at in the last cha|> 

 ter to organic beings in a state of nature, we must briefly dis- 

 cuss whether these latter are subject to any variation. To 

 treat this subject at all properlj^ a long catalogue of dry facts 

 ought to be given; but these I shall reserve for my future 

 work. Nor shall I here discuss the various definitions which 

 have been given of the term species. No one definition has 

 as yet satisfied all naturalists ; yet every naturalist knows 

 vaguely what he means when he speaks of a species. Gen- 

 erally 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 devia- 

 tion of structure, generally injurious to or not useful to the 

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

 cal sense, as implying a modification directly due to the physi- 

 cal conditions of life ; and " variations " in this sense are sup- 

 posed not to be inherited : but who can say that the dwarfed 

 condition of shells in the brackish waters of the Baltic, or 

 dwarfed plants on Alpine summits, or the thicker fur of an 

 animal from far northward, would not in some cases be inher- 

 ited for at least some few generations ? and in this c;ise I 

 presume that the form would be called a variety. 



It may be doubted whether sudden and great deviations of 

 structure such as we occasionally see in our domestic produc- 



