. Principes du zoo économique ?logie. Zoologie, économique. Holothurides 01 ale plus ver-comme en apparence. Certains sont si longs et fins qu'ils sont parfois considérés comme des vers. La taille varie d'un pouce dans le cas d'une espèce trouvée sur la côte du Massachusetts, à 3 pieds, dans une autre espèce trouvés dans la baie de Monterey, Californie. La paroi du corps est dure, coriace, musclé, et pas aussi rigide que dans l'étoile de mer ou d'oursin, bien que minute spicules calcaires sont dispersés dans tout cela. Le tube-pieds peut être en rangées, ou dispersés, ou entièrement veulent- ing, selon les espèces, dont plusieurs hundr

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. Principles of economic zoo?logy. Zoology, Economic. HOLOTHUROIDEA 01 ale more worm-like in appearance. Some are so long and slender that they are sometimes thought to be worms. The size varies from inch in one species found upon the Massachusetts coast, to 3 feet, in another species found in Monterey Bay, California. The body wall is tough, leathery, muscular, and not so rigid as in the starfish or sea-urchin, although minute calcareous spicules are scattered throughout it. The tube-feet may be in rows, or scattered, or entirely want- ing, depending upon the species, of which several hundred are recorded. The sea-cucumbers move with their long axis parallel to the ground. They creep along with the help of the tentacles. Protective Resemblance.— Their colors, which are reddish brown or yellowish, harmonize so closely with those of their en- vironment that their protective resemblance is almost perfect. As the animals rest on the bot- tom of the sea with their feathery tentacles spread out they closely resemble the vegetation of the sea bottom. A person may stand within a foot of the sea- cucumber and not see it. The alimentary tube (Fig. 47) is several times the length of the animal, and the intestine is coiled in a uniform manner. The food of the holothurians consists of organic matter obtained from the sand which they swallow, or of small animals which they capture with their tentacles. They are nocturnal in their feeding habits, resting quietly during the day on the bottom of the sea or buried in the sand. The respiratory system consists, probably, of the so-called " respiratory trees, " two hollow, much-branched organs open- ing into the cloaca, which is periodically filled with water.. Fig. 47.—Sea-cucumber {Holo- thurian) dissected to show ali- mentary tube, al.t. (Leuckart.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati

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