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 Dispersion.--Questions Raised by Agassiz.--Conclusions of Cope.--Questions Raised by Cope.--Views of Günther.--Fresh-water Fishes of North America.--Characters of Species.--Meaning of Species.--Special Creation Impossible.--Origin of American Species of Fishes. 282 CHAPTER XVII. DISPERSION OF FRESH-WATER FISHES. (_Continued._) Barriers to Dispersion of Fresh-water Fishes: Local Barriers.--Favorable Waters Have Most Species.--Watersheds.--How Fishes Cross Watersheds.--The Suletind.--The Cassiquiare.--Two-Ocean Pass.--Mountain Chains.--Upland Fishes.--Lowland Fishes.--Cuban Fishes.--Swampy Watersheds.--The Great Basin of Utah.--Arctic Species in Lakes.--Causes of Dispersion still in Operation. 297 CHAPTER XVIII. FISHES AS FOOD FOR MAN. The Flesh of Fishes.--Relative Rank of Food-fishes.--Abundance of Food-fishes.--Variety of Tropical Fishes.--Economic Fisheries.--Angling. 320 CHAPTER XIX. DISEASES OF FISHES. Contagious Diseases: Crustacean Parasites.--Myxosporidia or Parasitic Protozoa.--Parasitic Worms: Trematodes, Cestodes.--The Worm of the Yellowstone.--The Heart Lake Tape-worm.--Thorn-head Worms.--Nematodes.--Parasitic Fungi.--Earthquakes.--Mortality of Filefish. 340 CHAPTER XX. THE MYTHOLOGY OF FISHES. The Mermaid.--The Monkfish.--The Bishop-fish.--The Sea-serpent. 359 CHAPTER XXI. THE CLASSIFICATION OF FISHES.