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 Insessores on one side., and into the Gral- 

 latores on the other; while in the other column the 

 Scansores, in like manner, blend into the Conirostres, 

 although connected also with the Tenuirostres. 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 Grallatores resemble the Tenui- 

 rostres in having very small mouths, and long soft 

 bills. Finally, the Scansores 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 

 compared 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. 



