232 FIRST PRINCIPLES OF NATURAL CLASSIFICATION. 
exhibits the orders or first divisions of birds; the 
second, the tribes of one of these orders, namely, the 
Insessores, or perching birds. Each of these is a cir- 
cular group: for in one column we find the Rasores 
pass into the Jnsessores on one side, and into the Gral- 
Jatores on the other; while in the other column the. 
Scansores, in like manner, blend into the Conirostres, 
although connected also with the Tenuwirostres. We 
shall now show in what way each of these parallel 
series analogically agree in the details of their cor- 
responding points, in some one or more remarkable 
peculiarities of structure. The Insessores and the Co- 
nirostres, besides being the most perfectly organised in 
their respective groups, are remarkable for the com- 
parative smallness of the notch or tooth of their bill: 
here, then, is their analogy. In the Raptores and the 
Dentirostres, the notch is so large as to assume the 
shape of a tooth, a peculiarity which belongs to these 
alone. The Natatores and Fissirostres again preserve 
the same chain of analogy by the smallness and slight 
developement of their feet, and by possessing the greatest 
powers of flight. The Grailatores resemble the Tenui- 
rostres in having very small mouths, and long soft 
bills. Finally, the Scansoves and the Rasores are the 
most intelligent and docile of all birds, and have a short 
thick bill, generally entire at the tip. Now as these re- 
semblances of analogy are totally independent of the 
affinity between the groups in each of these two columns, 
and as they follow each other precisely in the same or- 
der, there is, so far, analogical demonstration that this 
arrangement is natural. Here, then, the difference be- 
tween affinity and analogy is exemplified. Analogies 
will be more or less apparent, according as the groups 
eompared are of equal value, and approximate to each 
other‘in the general system. On the other hand, they 
will be more or less faint, and difficult to be traced, as 
the groups differ in value, and are remote. In speaking 
generally of affinity and analogy, we must always take 
into consideration the nature of the groups compared. 
