io8 TYPES OF ANIMAL LIFE 



possible to suppose that animals as diverse as frogs 

 and those monkey-like animals the lemurs, could have 

 gained this similarity of parts by inheritance. It is 

 obviously a case of " the independent origin of similar 

 structures." 



A very instructive change takes place in the develop- 

 ment of the frog in those structures which answer to our 

 own bone of the tongue. This bone in us consists of a 

 median central portion and two pairs of processes called 

 the greater (or hinder), and the lesser (or anterior) horns. 

 The young tadpole has, as fishes have, a series of arches 

 on either side of the throat supporting its gills. As the 

 animal develops these arches grow smaller and smaller, 

 till in the adult frog there comes to be a tongue bone, 

 with two pairs of processes or " horns " as in ourselves. 

 It is the hinder pair of '• horns " of the frog which 

 are formed from its gill arches, and thence we learn that 

 in our own pair of hinder, or greater, " tongue-bone 

 horns " we have what answers to the gill arches of tad- 

 poles and of fishes. Such is the case, because the gill 

 arches of fishes answer to the gill arches of the tadpole. 



Having now passed in review the more interesting 

 forms of frogs and toads — the order Aiioura — it is time 

 to inquire what are the creatures which form the second 

 order of the Batrachia ? As they all have long tails the 

 name of their order is UrodeJa, or, as it is sometimes 

 called, Caudata. Some such creatures are to be found in 

 most ponds in England and are familiar animals to every 

 schoolboy, and are known as efts or newts. The whole 

 world contains a hundred and one difterent kinds of them, 

 but of these no less than fifty-five species are found in 

 North America, while Australia and tropical Africa have 

 neither of them a single species. Only two are found in 

 the Indian region, and but nine, or at most ten, in tro- 



