Some jellyfishes are so poisonous that they are most dangerous even to man. Only one of these, however, is found in the North Atlantic, almost all the jellyfishes that one finds lying about on the beach being perfectly harmless. But if, when you are bathing, you see a yellowish-brown jellyfish about as big as a soup-plate swimming near you in the water, be sure to get out of its way as fast as you possibly can; for if its threads should touch any part of your body, you are almost sure to be very badly stung. There is very little doubt, indeed, that many swimmers have been killed by these creatures; while thousands of unwary bathers have been laid up for days, or even weeks, from the effects of their poison.
Sea-Anemones
What beautiful creatures are these—just like flowers growing under the sea! Some are like dahlias, some like chrysanthemums, and some like daisies, of all shades of crimson, and purple, and orange, and green, and it is very hard to believe that they are really living animals.
The tentacles of these creatures, which look so like the petals of flowers, are set with little cells containing poisoned darts, just like the fishing-threads of the jellyfishes. They can be spread out or drawn back into the body at will, and when they have all been withdrawn the anemone seems to be nothing more than a shapeless lump of colored jelly.
Anemones spend the greater part of their lives clinging to the surface of a rock at the bottom of the water, the broad base of the body acting just like a big sucker. They can crawl about, however, at will, and sometimes they will rise to the surface of the sea, turn upside down, hollow their bodies into the form of little boats, and then float away, perhaps for quite a long distance.
But few sea-anemones are seen on our eastern coast, because, except in the cool north, there are few rocks. On the warmer and rockier shores of California and northward, however, these lovely creatures occur in great variety.
Corals
Last upon our list come those most wonderful little creatures which are known as corals.
These are often called coral insects, but that is a great mistake. For they have nothing to do with insects at all, and are as different from them in every way as they can possibly be. They are properly called polyps, and we can best describe them, perhaps as very small sea-anemones. But they have one property which the anemones do not possess, namely, the power of extracting lime out of the sea-water and building it up round themselves in the form of coral.
These creatures may be roughly divided into two groups, the one consisting of the simple corals, which only live together in very small numbers, and the other of the reef-builders, which live in vast colonies, and build up masses of coral of enormous size. The latter are by far the more interesting, and the way in which they build up immense banks of coral is very wonderful indeed.