CHAPTER II 



Variation Under Nature 



Variability — Individual differences — Doubtful species — Wide ranging, 

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

 larger genera in each country vary more frequently than the 

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

 genera resemble varieties in being very closely, but unequally, 

 related to each other, and in having restricted ranges. 



B 



EFORE applying the principles arrived at in the last 

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

 briefly discuss 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 reserve for a 

 future work. Nor shall I here discuss the various definitions 

 which have been given of the term species. No one defini- 

 tion has 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 diffi- 

 cult to define ; but here community of descent is almost uni- 

 versally 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 consid- 

 erable deviation of structure, generally injurious, or not use- 

 ful to the species. Some authors use the term "variation" in 

 a technical sense, as implying a modification directly due to 

 the physical conditions of life; and "variations" in this sense 

 are supposed 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 northwards, would not in some 

 cases be inherited for at least a few generations ? and in this 

 case I presume that the form would be called a variety. 

 It may be doubted whether sudden and considerable devi- 



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