xiv Contents 



CHAPTER XXIV. 



THE EVOLUTION OF FISHES. 



PAGE 



The Geological Distribution of Fishes.— The Earliest Sharks.— Devonian 

 Fishes.— Carboniferous Fishes.— Mesozoic Fishes.— Terliary Fishes.— Fac- 

 tors of Extinction.— Fossilization of a Fish.— The Earliest Fishes.— The 

 Cyclostomes.— The Ostracophores.— The Arthrodires.— The Sharks.— 

 Origin of the Shark.— The Chima;ras.— The Dipnoans.— The Crossopte- 

 rj-gians. — The Actinopteri. — The Bony Fishes 435 



CHAPTER XXV. 



THE PROTOCHORD.\T.\. 



The Chordate Animals. — The Protochordates. — Other Terms Used in Classifi- 

 cation. — The Enteropneusta. — Classification of Enteropneusta. — Family 

 Harrimaniidae. — Balanoglossida;. — Low Organization of Harrimaniids 460 



CHAPTER XXVL 



THE TUNICATES, OR ASCIDI.-\NS. 



Structure of Tunicates. — Development of Tunicates. — Reproduction of Tuni- 

 cates. — Habits of Tunicates. — Larvacea. — .-^scidiacea.- Thaliacea. — Origin 

 of Tunicates. — Degeneration of Tunicates 467 



CHAPTER XXVII. 



THE LEPTOCWRDII, OR L.^NCELETS. 



The Lancelet. — Habits of Lancelets. — Species of Lancelets. — Origin of Lance- 

 lets 482 



CHAPTER XXVIII. 



THE CYCLOSTOMES, OR LAMPREYS. 



The Lampreys. — Structure of the Lamprey. — Supposed Extinct Cyclostomes. — 

 Conodontes.— Orders of Cyclostomes. — The Hyperotreta, or Hagfishes. — 

 The Hyperoartia, or Lampreys.— Food of Lampreys. — iNIetamorphosis of 

 Lampreys.— Mischief Done by Lampreys.— Migration or "Running" of 

 Lampreys.— Requisite Conditions for Spawning with Lampreys.— The 

 Spawning Process with Lampreys.— What Becomes of Lampreys after 

 Spawning? ^86 



