150 REED-SPARROW. 



omission. See British Zoology last published, 

 p. 16 1 . 



I have somewhat to advance on the different 

 manners in which different birds fly and walk ; 

 but as this is a subject that I have not enough 

 considered, and is of such a nature as not to be 

 contained in a small space, I shall say nothing 

 further about it at present 2 . 



No doubt the reason why the sex of birds in 

 their first plumage is so difficult to be distinguished 

 is, as you say, " because they are not to pair and 

 discharge their parental functions till the ensuing 

 spring." As colours seem to be the chief external 

 sexual distinction in many birds, these colours do 

 not take place till sexual attachment begins to 

 obtain. And the case is the same in quadrupeds ; 

 among whom, in their younger days, the sexes 

 differ but little ; but, as they advance to maturity, 

 horns and shaggy manes, beards and brawny 

 necks, &c. &c. strongly discriminate the male 

 from the female. We may instance still further 

 in our own species, where a beard and stronger 

 features are usually characteristic of the male 

 sex ; but this sexual diversity does not take place 

 in earlier life; for a beautiful youth shall be so 

 like a beautiful girl, that the difference shall not 

 be discernible : 



" Quern si puellarum insereres choro, 

 Mire sagaces falleret hospites 

 Discrimen obscurum, solutis 

 Crinibus, ambiguoque vultu." HOR. 



1 See Letter XXV. Part I. 



2 See Letter XLII. Part II. 



