326 INTRODUCTION TO ZOOLOGY. 



Sucli are the principles which seem now to he generally 

 recognised, even when there exists considerable difference of 

 opinion as to the details hy which they can most successfully 

 be reduced to practice. The following arrangement is that 

 which has been adopted by some of our leading British 

 ornithologists: 



Order I. RAPTORES -Birds of Prey, as Vultures, Eagles, Owls. 

 II. INSESSORES Perchers, as Sparrows, Linnets, Crows. 



III. RASORES Scraping Birds, as Pheasants, Fowls. 



IV. GRALLATORES Waders, as Herons, Bitterns. 



V. NATATORES Swimmers, as Geese, Divers, Gulls. 



According to the general plan we have pursued, we should 

 commence with the swimming birds, and gradually ascend to 

 that group which contains the Falcons and the Eagles, which 

 are regarded as the nobles and the kings of the feathered 

 tribes; but the birds usually placed lowest in the scale, such 

 as Gulls and Terns, do not present the slightest resemblance 

 to the creatures which rank highest, and were the last men- 

 tioned in the preceding class. Between certain mollusca and 

 fishes we found so great a resemblance, that a question had 

 arisen as to whether a certain species should be regarded as a 

 mollusk or a fish: between fish and reptiles, again, a similar 

 difficulty occurred; but between reptiles and birds, or between 

 birds and mammalia, there can be no such question. The 

 separation is so well marked, that there is no debateable 

 ground, no border territory. The birds stand out apart from 

 the groups on either side, distinctly isolated. No advantage, 

 therefore, accrues from placing the lowest of the birds next 

 to the reptiles, nor those regarded as the highest next to 

 the quadrupeds. Such an arrangement is also open to the 

 objection, that by most writers the different classes are treated 

 of in the order in which they have been here enumerated; 

 and it is desirable that the learner should be accustomed to 

 the same succession of family and genera, in this elementary 

 work, that he will meet with in those of a higher character. 

 For these reasons we have resolved on following the course 

 that is most generally pursued, and beginning with, the birds 

 of prey. 



