CONTENTS. VU 



PAGE 



Coolotnati from the Aecelomi. — Mantled Animals {Tunicata) and 

 Chorda- Animals {OTiordonia) . — Seventh Stage: Sofl-Worms (Scole. 

 cida). — A Side Branch of the latter: the Acorn-Worm {Balano- 

 glossus). — Differentiation of the Intestinal Tube into Gill-intes- 

 tine and Stomach-intestine. — Eighth Stage : Chorda- Animals (Clwr- 

 donia). — Ascidian Larva exhibits the Outline of a Chorda-Animal. — 

 Construction of the Notochord. — Mantled Animals and Verte- 

 brates as Diverging Branches of Chorda-Animals. — Separation of 

 Tertehrates from the other Higher Animal Tribes (Articulated 

 Animals, Star-Animals, Soft-bodied Animals). — Significance of the 

 Metameric Formation. — Skull-less Animals (Acrania) and Skulled 

 Animals {Oraniota). — Ninth Ancestral Stage : Skull-less Animals. 

 — Amphioxus and Primitive Vertebrate. — Development of Skulled 

 Animals (Construction of the Head, Skull, and Brain). — Tenth 

 Ancestral Stage : Skulled Animals, allied to the Cyclostomi (Myxi- 

 noidce aui Petromyzonidce) .,, ... .,, „, ... 71 



CHAPTER XVIII. 



THE PEDIGREE OP MAN. 



III. From ths Pbimitive Fish to the Amniotic Animal. 



Comparative Anatomy of the Vertebrates. — The Characteristic Qualities 

 of the Double-nostrilled and Jaw-monthed ; the Double-Nostrils, 

 the Gill-arch Apparatus, with the Jaw.arches, the Swimming- 

 bladder, the Two Pairs of Limbs. — Relationship of the Three 

 Groups of Pishes : the Primitive Pishes (_Selachii), the Ganoids 

 (Ganoides), the Osseous Fishes (Teleostei). — Dawn of Terrestrial 

 Life on the Earth.— Modification of the Swimming-bladder into 

 the Lungs. — Intermediate Position of the Dipneusta between the 

 Primitive Pishes and Amphibia. — The Three Extant Dipneusta 

 (Protopterus, Lepidosiren, Oeratodus) . — Modification of the Many- 

 toed Pin of the Pish into the Pive-toed Foot. — Causes and Effects 

 of the latter. — Descent of all Higher Vertebrates from a Five-toed 

 Amphibian. — Intermediate Position of the Amphibians between the 

 Lower and Higher Vertebrates. — Modification or Metamorphosis of 

 Progs. — Different Stages in Amphibian Metamorphosis. — The 

 Gilled Batrachians (Proteus and Axolotl). — The Tailed Batrachians 

 (Salamanders and Mud-fish). — Frog Batrachians (Frogs and 

 Toads). — Chief Group of the Amnion Animals, or Amniota (Reptiles, 

 Birds, and Mammals). — Descent of all the Amniota from a Common 



