CLASS AMPHIBIA. 



CHAPTER I. 

 FEOGS AND TOADS. 



Characteristics of Amphibians Remarkable Skin The Skeleton Heart of Frog Circulation of the Blood Method of 

 Respiration Gills, or Branchiae The Nervous System Brain of Fros The Eyes and Ears Alimentary Canal THE 

 ANOURA, OR THE FROGS AND TOADS Distinctive Features -Hibernation Lungs Throat sacs Teeth Food 

 Skeleton Muscles of Thigh and Leg Batrachian Locomotion Their Swimming Powers The Tongue The Croak- 

 ings Metamorphosis of the Frog Structure of the Tadpole Circulation of Blood in the Gills Last Stages of the 

 Tadpole Condition THE BATRACHIAKS WITHOUT TONGUES The Surinam Toad Birth of the Young Pipas THE 

 BATRACHIANS WITH TONGUES THE OXYDACTYLA THE RANID.E, TRUE FROGS The Common Frog Habits Its Rela- 

 tions with Humanity Development of the Embryo The Frog's Skull The Edible Frog The American Bull Frog 

 African and other Frogs The Horned Ceratophrys THE PELOBATID^E The Obstetric Frog The Bombinator 

 Igneus The Brown Mud Frog The Globose Cacopus Frog THE BUFONIM: The Common Toad Habits The Meta- 

 morphosis The Toad lias not Escaped Calumny The so-called Venom The Natter- Jack, or Rush Toad The Variable, 

 or Green Toad The Indian and African Toads Mr. Darwin on a South American Toad The North American 

 Toads The Breviceps THE DISCODACTYLES THE TREE FROGS The Hyloranae The Hylidae Their Digits The 

 Common Hyla The Goose-footed Hyla The Elegant Hyla The Common Golden Tree Frog The Pouched Frog 

 The Common Indian Tree Frog The Spurred Tree Frog Tree Frogs of Ceylon The Acris gryllus The Genus 

 Rhacophorus The Hylodes ocularis The Martinique Frog The Phyllomedusidse The Great Green Tree Frog 

 The Dendrobatidse The Genus Plectropus. 



THE vertebrated animals called Amphibia were, as has been already noticed in the Introduction 

 to the Reptilia, formerly included with the Reptiles in a great division of the animal kingdom ; now 

 they are placed in a class by themselves, and they have many structural resemblances to the Fish. 

 They are cold-blooded, and their skin is generally naked. They have limbs (with few exceptions), and 

 breathe by means of lungs, or they have more or less persistent gills. Their circulation is incom- 

 plete in comparison with that of the Vertebrata already noticed, and the skull joins with the first 

 vertebra by means of two occipital condyles. Finally, the Amphibia, with few exceptions, have 

 an immature or a larval and an adult condition, the first being passed in water, and certain 

 membranes are deficient in the embryo, or unborn. The general shape of the Amphibia indicates 

 that they are fashioned to exist, at some time of their lives, in water and on land, and the 

 body is long and cylindrical, or short and compressed, and frequently there is a long, flat tail, 

 and a back crest of skin. Sometimes there are no limbs for instance, in the worm- or snake- 

 like Caecilias; in other instances, as in the Siren, there are only short fore limbs, or else the 

 rudiments of fore and hind limbs furnished with weak and limp digits. Even in those kinds which 

 have the limbs and digits well developed, they act principally in pushing the heavy, low body along 

 on the feet. The Batrachians Frogs and Toads which have short trunks, tailless in adult age, 

 are the only Amphibia which have two pairs of long and useful active members, which enable their 

 possessors to run, jump, swim, and climb. The skin is of vast importance to the Amphibia as a secre- 

 ting and a respiratory surface, and it is usually smooth and clammy, or viscid ; but the CaBcilias alone, 

 amongst existing Amphibians, have small scales or scutes imbedded in it, and they present the rayed 

 appearance of fish-scales. The skin includes, as a rule, many glands which are either simple and flask- 

 shaped ; and they assist, by their secretion, in the process of moulting, or they may be composed of a 

 number of sac-like bodies, and in this case the secretion is often acrid and foetid, and is fatal to small 

 creatures ; and, when not so, it is equally viscid, and lubricates the surface and makes it slimy. These 

 complicated glands are collected at certain parts of the body, especially near the back of the jaw in 

 the parotid region, in Toads and Salamanders, and also on the sides of the body and on the hind limbs. 

 The colour of the skin and its shades are produced by colouring granules which are situated in the 

 epidermal cells, and also by the presence of very large branched pigment cells in the skin, which, as in 

 the Frogs, for instance, produce changes in colour by alterations in their shape and position. With 

 regard to the bones of the skull and skeleton, it is remarkable and significant, that in these low 

 Vertebrates they can be compared with and named from those of the higher animals. The bodies 

 of the vertebrae are of bone, and there are intervertebral cartilages ; there are also relics of the noto- 

 chord, an embryonic condition of the vertebral column. The shape of the body of the vertebra differs 

 in the various groups. The sacrum rarely consists of more than one vertebra, but there are exceptions. 

 With regard to the skull, the base and part of the sides are differently arranged to the correspond- 

 ing regions in the Reptiles and higher Vertebrates, for the Amphibia have not complete basi- 



