Once, when poling my boat over the great coral reef of the outer Florida Keys I came upon a little plot of seaweed in shallow water which was so covered with huge sea cucumbers (Fig. 58) that it would have been an easy matter to fill the boat. They were from six to twelve inches in length, two or three inches across, and bore a striking resemblance to actual cucumbers. In color they were brown, and when lifted from the water they slowly moved or twisted, sending out a stream of water. They might have been made of leather, so far as any evidence of life was concerned, and were so tough that a spear thrust into one had to be cut away, so tenacious was the hide of this singular sluglike animal. Taking a large one from the bottom, I placed it in a glass jar standing on the deck of my boat, whereupon a very singular occurrence took place. When the air began to be exhausted in the water of the glass, out from the sea cucumber came a long, slender fish, so ghostly and ethereal that when it died, as it did almost immediately, I placed it upon a piece of newspaper and read print through its body. The fish was known as Fierasfer, and it lived in the long intestine of the sea cucumber. Since then the fish has been closely studied in the Naples Aquarium, where it had the same habit, and where the attendant naturalists saw the fish come out, and return tail first.

The great sea cucumber of Florida may be taken as a type of all the group which differ mainly in size, color, and shape. Some are very short and have a decided flat lower surface; others are long, fragile, and easily broken; and many are brilliant in color. Nearly all are famous for their singular and often beautiful breathing organs which protrude from the mouth and bear the most remarkable resemblance to plants. In many specimens of the Atlantic Pentacta (Fig. 58), kept in an aquarium, this resemblance was very marked, as the animals at once buried themselves in the sand from which beautiful plants seemingly grew, being merely the breathing organs of the wily mimic. These organs vary much in size and beauty. In some species they are very elaborate, in others they are simple, flowerlike objects. The greatest variation is found in them. In one which I observed the tentacles resembled small toadstools.

Many of the sea cucumbers, or holothurians, are very sensitive, and when captured will often cast off their various organs. This does not indicate the death of the animal, as they are soon replaced. A singular trait of the long glasslike Synapta is that of cutting itself in two when starved. At first an end of the animal is dropped, then another piece, and this is continued until nothing but the mouth remains, everything having seemingly been sacrificed to save this portion. If food is now supplied, this animal will soon recover and assume its normal condition.

Synapta has no feet, their place seemingly being taken by peculiar limy spicules, shaped like anchors (Fig. 59), which are deeply buried in the skin. In its structure the sea cucumber resembles its cousins the starfishes and sea urchins, and standing on end, may be compared to an elongated sea urchin. Nothing can be more uninviting than these animals, and when dried the flesh has the consistency of leather. Yet the sea cucumber is highly regarded by the Chinese as a delicacy, and the Malays have a large fleet engaged in the business of gathering and preparing them. The animals are collected and dried, then smoked and packed in bales and sent to China. They may be found in any of the markets of these people, in San Francisco and New York. About the Pacific island of Santa Catalina they are very commonly seen through the bottom of the glass-bottomed boats, lying in the seaweed and imitating it in color.