﻿33 6 ON THE CLASSIFICATION OF BIRDS. 



in its analogies ; for this may be done by simply show- 

 ing that no animal yet known that is excluded from the 

 group has an affinity with the type equal to any of 

 those that are brought within the group. Our doctrine 

 of analogies may thus, to use a colloquial expression, be 

 thrown overboard, and yet our group will remain just 

 as natural as it was, if the chain of affinity has been 

 truly and strictly followed. 



CHAP. IL 



GENERAL REMARKS ON THE INSESSORIAL OR PERCHING OR- 

 DER. PRIMARY DIVISIONS. CHARAACTERS AND ANALO- 

 GIES OF THE DENTI ROSTRAL TRIBE. 



(271.) The order Insessores, composed of the perch- 

 ing birds, is the most numerous, and the most varied, in 

 the whole circle of ornithology. It comprises, as before 

 stated, all those tribes and families which (without being 

 rapacious) live habitually among trees, or at least have 

 nothing in their structure to show they are in the least 

 degree aquatic. Their foot, in short, as the name 

 denotes, is especially formed for grasping or perching ; 

 a peculiarity evinced by the situation of the hinder toe, 

 which is invariably placed upon the same level, or 

 plane, as those in front. Their number is generally 

 four ; either placed, as in ordinary birds, three forwards 

 and one backwards, or, as in the scansorial tribe, two in 

 front and two behind. The length of the tarsus or 

 shank is always moderate, and generally very short 

 in comparison to what is seen in the other orders ; and, 

 as these birds never seize their prey by the claws, 

 these weapons are never retractile. The perchers are 

 thus distinguished from the birds of prey, properly so 

 called ; while the situation of the hind toe separates them 



