VARIATION OF CHARACTERS. 241 



determined, whereas habits are only to be traced 

 from the living subject. Every one, for instance, 

 can see whether a bird has its claws acute and very 

 much curved, or whether they are comparatively 

 straight and obtuse : now we know, from observ- 

 ation, that these modifications indicate two very 

 different habits ; the first belonging to birds which 

 always perch upon boughs, and the latter distinguish- 

 ing such as live chiefly upon the ground. These 

 habits, however, can never be known to the student 

 as matters of fact, who merely sees such birds in a 

 museum : we are therefore to direct his attention, 

 in the first place, to circumstances or characters 

 which it is in his power to see and verify ; and 

 afterwards to show the particular influence of such 

 characters on habits and economy. 



(166.) The essential or most prevalent characters 

 of our group, as a whole, having been ascertained, 

 we are then to examine it more in detail, tracing 

 the mode in which these characters vary, and as- 

 certaining how far, and in what way, this variation 

 is accompanied by a difference of habit and economy. 

 There is, for instance, a whole family of beetles 

 (the Petalocera Saprophaga of M'Leay) which 

 feed on living vegetables, in contradistinction to 

 another, which devour them only in a decayed or 

 putrescent state : but among those which agree in 

 feeding upon living plants, we find some restrict 

 their diet to the petals of flowers, others select only 

 the green leaves, and many live upon the juices of 

 the stem. Here, then, we have modifications of the 

 same habit; and it is our business to trace such 

 variations, whether in form or in economy, through 



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