In tropical seas some fish are found to be always poisonous wherever and whenever caught, but there are numerous instances where wholesome fish become noxious when found in certain localities, especially on coral reefs and shoals. Fish when feeding on decomposing coral polyps, medusæ, and poisonous mollusks found on these reefs often become noxious, as the following instance will prove: Midway between Cuba, Hayti, and Jamaica lie the extensive reefs and shoals of the Formigas, which are several miles in extent and covered by a small depth of water. These shoals present a concentration of all the incidents to be found in West Indian fringing shore reefs. Arborescent corals and spreading millepores stretch on walls and ledges, interspersed with huge meandrinas and brainstones, among which lodge a profusion of _Holothurias_, starfishes, and a variety of sponges. This great mass of reefs, called from their clustering swarm the Ants' Nest, or the Formigas, abound with all sorts of fishes. As you approach the great submarine plateau, the odor of the slime and of the spermatic substances that find a resting place in the crevices and shallow pools spread through it is very remarkable--the pleasant blandness of the sea breeze suddenly changing to the nauseating smell of a fish market. Those who have waded on tropical shore reefs know not only the strong scent given out by the polyps that build there, but feel how sensibly the hands are affected, and how the skin of the thighs is susceptible of a stinging irritation from the slightest contact with the slime of corals. It has been found by invariable experience that all the fishes taken on the Formigas are pernicious; that the barracudas especially are always poisonous. Similar stretches of shoals among the Bahamas produce fishes deleterious as food. The low-spreading ledges and banks of the Virgin Islands, called the Anegadas, or the Drowned Islands, afford a similar unfavorable ground for fishing. In this way we may account for the remark of Dr. Grainger that fishes are poisonous at one end of St. Christopher while they are harmless at another. We get over, by these several incidents of those fishing grounds, the adventitious occurrence of poisonous among wholesome fishes, which become deleterious from the food on which they subsist at certain seasons on certain banks and coasts.