SPECIES. 259 



shoals, flat, sandy, muddy, or rocky coasts, limestone 

 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. ; 

 3rd, in their dependence upon this or that kind of food 

 for their sustenance; 4th, in the duration of their life; 

 5th, in the mode of their association with one another, 

 whether living in flocks, small companies, or isolated; 

 6th, in the period of their reproduction ; 7th, in the 

 changes they undergo during their growth, and the pe- 

 riodicity of these changes in their metamorphosis ; 8th, 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 to 

 which animals attain, in the proportions of their parts to 

 one another, in their ornamentation, etc., and ah 1 the 

 variations to which they are liable. 



As soon as all the facts bearing upon these different 

 points 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, which add nothing 

 to our real knowledge, and only go to swell the nomen- 

 clature of animals and plants, already so intricate. 



Assuming, then, that species cannot always be identified 

 at first sight, and that it may require a long time and 

 patient investigation to ascertain their natural limits ; 

 assuming further, that the features alluded to above are 

 among the most prominent characteristics of species, we 

 may say that species are based upon well determined 



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