INTRODUCTION. 11 



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 diflferent — 

 some 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 organisation in all the others; 

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

 internal organs. 



* Carus, Vergleich. Zoot Erst. Theil., p. 35. 



