CONTENTS ix 



CHAPTER II 



PAGE 



Evolution and Geological History 170 



The earliest Amphibia, the extinct Labyrinthodonts. Absence of tran- 

 sitional forms in the Secondary Formations. Number of Amphibia 

 in comparison with other classes. 



CHAPTER III 



Distribution and Habits 178 



Amphibia usually associated with stagnant fresh water. Geographical 

 distribution. Notogaea and Arctogaea. Oceanic and other islands. 

 Food and feeding. Relations to salt and moisture. ^Estivation and 

 hibernation. 



CHAPTER IV 

 Reproduction ............ 183 



Tail-less Batrachia, general course of development. Various modes of 

 protecting the eggs : nests in the water and on land. Eggs carried 

 by the parents, round the legs by the male, on the skin or in a dorsal 

 pouch by the female, in enlarged vocal sacs by the male. Pairing in 

 Urodela. Protection of eggs by Urodeles. Salamanders that 

 carry their eggs. Viviparous salamanders. 



CHAPTER V 

 Variation and Adaptation ......... 210 



Metamorphosis and occasional "persistence of the larval condition 

 (Neoteny). History of the axolotl and its explanation. Colour: 

 protective and warning coloration. Adaptations for locomotion. 

 Adhesive discs of tree-frogs. The spade of Pelobates. Respiratory 

 adaptations : salamanders with neither lungs nor gills. Allantoic 

 gills in embryos. Adaptations in the male for pairing. Convergent 

 evolution in tree-frogs. 



SECTION III 

 Fishes 



By J. T. Cunningham, M.A., Oxon. 



CHAPTER I 



Introductory 231 



Definition. General characters. Position in the Animal Kingdom and 

 Classification. 



CHAPTER II 



Evolution and Paleontology 249 



The extinct Ostracoderms. Fossil Elasmobranchs. Crossopterygians 

 and Dipnoi evolved in fresh water. Pedigree of Teleostomi. 

 Relative abundance of different orders in past and present times. 



