REPTILES AND BIRDS. 



INTRODUCTORY. 



There is little apparent resemblance between the elegant feathered 

 warbler wbicb makes the woods re-echo to its cheerful song, and 

 the crawling reptile which is apt to inspire feelings of disgust when 

 the more potent sensation of terror is absent — between the familiar 

 Swallow, which builds its house of clay under the eaves of your 

 roof, or the warbler whose nest, with its young progeny, care- 

 fuUjr watched by the father of the brood in the silent watches of 

 the night, is now threatened by the Serpent which has glided so 

 silently into the bush, its huge mouth already open to swallow 

 the whole family, while the despairing and fascinated parents 

 have nothing but their slender bills to oppose to their formid- 

 able foe. "Placed side by side," says Professor Iluxley, "a 

 Humming-bird and a Toitoise, or an Ostrich and a Crocodile, 

 offer the strongest contrast ; and a Stork seems to have little 

 but its animality in common with the Snake which it swallows." 

 Nevertheless, unlike as they are in outward appearance, there 

 is sufficient resemblance in their internal economy to bring them 

 together in most attempts at a classification of the Animal King- 

 dom. The air-bladder which exists between the digestive canal 

 and kidneys in some fishes, becomes vascular with the form 

 and cellular structure of lungs in reptiles ; the heart has two 

 auricles, the ventricle in most is imperfectly divided, and more 

 or less of the venous blood is mixed with the arterial which 

 circulates over the body ; but retaining their gills and being 

 therefore transitional in structure, they are also cold-blooded. In 



B 



