INTRODUCTION. 19 



presence of lungs and articulated members, yet inferior to Birds from having cold 

 blood, a simple heart, and a less degree of sensibility, these animals, by their 

 multiplied and extremely diversified forms, make the medium of connexion between 

 beings of the most opposite character. The Testudo connects them with the 

 inferior Mammalia, as with the Armadillo, on the one hand, while the Siren 

 approximates them to the cartilaginous Fishes on the other. Serpents form a link 

 of another series, connecting this class with osseous Fishes, as with the Eel; and 

 the Flying Lizard connects them with the Birds.* In order to estimate properly 

 the rank these animals hold in the scale of creation, it is necessary to examine 

 the general and principal points of their organization — to study the number of 

 their senses, and their degree of perfection. Without this, we cannot understand 

 the diversified forms and the shades of life that present themselves in such infinite 

 variety among them. Their conformation and modes of life are so different — 

 some being organized for creeping, others for walking, for swimming, and even for 

 flying, that it would be impossible to generalize their anatomical forms or structure. 

 We cannot give the structure of one as the type of organization in all the others; 

 for their variation in shape and figure is attended with modifications of their 

 internal organs. These differences of structure will be fully described in the 

 anatomical part of this work; at this time, according to the plan proposed above, 

 it can only be said that the difference of organization observed in different 

 species, led Brogniart to arrange them all in four great orders — I. Chelonia. II. 

 Sauria. III. Ophidia. IV. Batrachia. 



* Carus, Vergleich. Zoot. Erst. Theil., p. 25. 



