Catfishes.—Venomous Spines.—The Lancet of the Surgeon-fish.—Spines of the Sting-ray.—Protection through Poisonous Flesh of Fishes.—Electric Fishes.—Photophores or Luminous Organs.—Photophores in the Iniomous Fishes.—Photophores of Porichthys.—Globefishes.—Remoras.—Sucking-disks of Clingfishes.—Lampreys and Hogfishes.—The Swordfishes.—The Paddle-fishes.—The Sawfishes.—Peculiarities of Jaws and Teeth.—The Angler-fishes.—Relation of Number of Vertebræ to Temperature, and the Struggle for Existence.—Number of Vertebræ: Soft-rayed Fishes; Spiny-rayed Fishes; Fresh-water Fishes; Pelagic Fishes.—Variations in Fin-rays.—Relation of Numbers to Conditions of Life.—Degeneration of Structures.—Conditions of Evolution among Fishes.

179 CHAPTER XIII. COLORS OF FISHES. Pigmentation.—Protective Coloration.—Protective Markings.—Sexual Coloration.—Nuptial Coloration.—Coral-reef Fishes.—Recognition Marks.—Intensity of Coloration.—Fading of Pigments in Spirits.—Variation in Pattern. 226 CHAPTER XIV. GEOGRAPHICAL DISTRIBUTION OF FISHES. Zoogeography.—General Laws of Distribution.—Species Absent through Barriers.—Species Absent through Failure to Maintain Foothold.—Species Changed through Natural Selection.—Extinction of Species.—Barriers Checking Movements of Marine Species.—Temperature the Central Fact in Distribution.—Agency of Ocean Currents.—Centers of Distribution.—Distribution of Marine Fishes.—Pelagic Fishes.—Bassalian Fishes.—Littoral Fishes.—Distribution of Littoral Fishes by Coast Lines.—Minor Faunal Areas.—Equatorial Fishes most Specialized.—Realms of Distribution of Fresh-water Fishes.—Northern Zone.—Equatorial Zone.—Southern Zone.—Origin of the New Zealand Fauna. 237 CHAPTER XV. ISTHMUS BARRIERS SEPARATING FISH FAUNAS. The Isthmus of Suez.—The Fish Fauna of Japan.—Fresh-water Faunas of Japan.—Faunal Areas of Marine Fishes of Japan.—Resemblance of Japanese and Mediterranean Fish Faunas.—Significance of Resemblances.—Differences between Japanese and Mediterranean Fish Faunas.—Source of Faunal Resemblances.—Effects of Direction of Shore Lines.—Numbers of Genera in Different Faunas.—Significance of Rare Forms.—Distribution of Shore-fishes.—Extension of Indian Fauna.—The Isthmus of Suez as a Barrier to Distribution.—Geological Evidences of Submergence of Isthmus of Suez.—The Cape of Good Hope as a Barrier to Fishes.—Relations of Japan to the Mediterranean Explained by Present Conditions.—The Isthmus of Panama as a Barrier to Distribution.—Unlikeness of Species on the Shores of the Isthmus of Panama.—Views of Dr. Günther on the Isthmus of Panama.—Catalogue of Fishes of Panama.—Conclusions of Evermann & Jenkins.—Conclusions of Dr. Hill.—Final Hypothesis as to Panama. 255 CHAPTER XVI. DISPERSION OF FRESH-WATER FISHES. The Dispersion of Fishes.—The Problem of Oatka Creek.—Generalizations as to