258 Natural History of the United States. 



stone banks, coral reefs, swamps, meadows, fields, dry lands, salt 

 deserts, sandy deserts, moist land, forests, shady groves, sunny 

 hills, low regions, plains, prairies, high table-lands, mountain 

 peaks, or the frozen barrens of the Arctics, etc. ; 3d. in their de- 

 pendence upon this or that kind of food for their sustenance ; 4th. 

 in the duration of their life ; oth. in the mode of their association 

 with one another, whether living in flocks, small companies, or 

 isolated; 6th. in the period of their reproduction; Yth, in the 

 changes they undergo during their growth, and the periodicity of 

 these changes in their metamorphosis ; 8tb, in their association 

 with other beings, which is more or less close, as it may only 

 lead to a constant association in some, whilst in others it amounts 

 to parasitism ; 9th, specific characteristics are further exhibited 

 in the size animals attain, in the proportions of their parts to one 

 another, in their ornamentation, etc. and all the variations to 

 which they are liable. 



" As soon as all tbe facts bearing upon these different point 3 

 have been fully ascertained, there can remain no doubt respecting 

 the natural limitation of species ; and it is only the insatiable 

 desire of describing new species from insufficient data which has 

 led to the introduction in our systems of so many doubtful species, 

 whicb add nothing to our real knowledge, and only go to swell 

 the nomenclature of animals and plants already so intricate. 



" Assuming, then, that species cannot always be identified at 

 first sight, that it may require a long time and patient investiga- 

 tions to ascertain their natural limits ; assuming further, that the 

 features alluded to above are among the most prominent charac- 

 teristics of species, we may say, that species are based upon well 

 determined relations of individuals to the world around them, to 

 their kindred, and upon the proportions and relations of their 

 parts to one another, as well as upon their ornamentation. Well 

 digested descriptions of species ought, therefore, to be compara- 

 tive ; they ought to assume the character of biographies, and at- 

 tempt to trace the origin and follow the development of a species 

 during its whole existence. Moreover, all the changes which 

 species may undergo in course of time especially under the fos- 

 tering care of man, in the state of .domesticity and cultivation, 

 belong to the history of the species ; even the anomalies and dis- 

 eases to which they are subject belong to their cycle, as well as 

 their natural variations. Among some species, variation of color 



