CHARACTERS OF ANIJJfcALS. 113 



CHAP. I. 



EXTERNAL CHARACTERS 



usually employ, as external characters, the 

 marks which are furnished by colour, dimensions, weight, 

 and shape. On each of these we shall now offer a few ob- 

 servations. 



1. Colour. This character, the most attractive to the 

 eye, has engrossed a great share of attention. In many 

 description, of birds, for example, it is the only character 

 which is employed, by ornithologists, in the discrimination 

 of species. But this character, we have seen, varies, in many 

 cases, with age, season, and sex ; so that an implicit reliance 

 on its indications, unless where the changes have been pre- 

 viously ascertained, must be apt to mislead. Accordingly, 

 we find individuals of the same species exhibiting different 

 coloured plumage, according to circumstances, which have 

 been exalted to the rank of species, and much confusion, 

 in consequence, introduced into the arrangements of the 

 ornithologist. Similar errors have been committed with spe- 

 cies of almost every class. Indeed it seems doubtful, whether 

 a species ought to be constituted from characters furnished 

 by colour alone. Even where the colours appear fixed, 

 other marks, of a less suspicious kind, will readily be de- 

 tected. 



It was for a long time a matter of regret among natural- 

 ists in general, that no uniform nomenclature for colours 

 was employed, so that it was frequently impossible, in the 



VOL. II. H 



