CHAPTER I. 



AMPHIBIA, OR BATRACHIANS. 



Those geographers who divide the world into land and sea over- 

 look in their nomenclature the extensive geographical areas 

 which belong permanently to neither section — namely, the vast 

 marshy regions on the margins of lakes, rivers, and ponds, which 

 are alternately deluged with the overflow of the adjacent waters, 

 or are parched from the exhalations produced by summer heat ; 

 regions which could only be inhabited by beings capable of living on 

 land or in water — beings having both gills (through which they may 

 breathe in water) and lungs (through which they may breathe on 

 land.) The first order of Reptiles possesses this character, and hence 

 its name of Amphibia, from a/*<f>l-j8fos, having a double life. 



The transition from Fishes to Reptiles is described by Professor 

 Owen, with that wonderful power of condensation which he possesses, 

 in the following terms : — " All vertebrates, during more or less of 

 their developmental life-period, float in a liquid of similar specific 

 gravity to themselves. A large proportion, constituting the lowest 

 organised and first developed forms of this province, exist and 

 breathe in water, and are called fishes. Of these a few retain the 

 primitive vermiform condition, and develop no limbs ; in the rest 

 they are 'fins' of simple form, moving by one joint upon the 

 body, rarely adapted for any other function than the impulse 

 or guidance of the body through the water. The shape of the 

 body is usually adapted for moving with least resistance through 

 the liquid medium. The surface of the body is either smooth and 

 lubricous or it is covered with overlapping scales ; it is rarely de- 

 fended by bony plates or roughened by tubercles. Still more 

 rarely is it armed with spines." Passing over the general economy 

 of Fishes we come to the heart. " The heart," he tells us, " consists 

 of one auricle receiving the venous blood, and one ventricle pro- 

 pelling it to the gills or organs submitting that blood in a state of 

 minute subdivisions to the action of aerated water. From the 

 gills the aerated blood is carried over the entire body by vessels, 



