These worms almost invariably select a sheltered situation for their abode, and should be searched for at the foot of rocks, or under stones, and it is no easy matter to move the buried tube with its occupant intact.
When turning over the stones of a sandy or muddy beach one frequently discovers the slender, thread-like tentacles of the Terebella, together with the sandy filaments that surround the mouth of the tube, the remainder of the tube and its occupant being beneath the surface, and the ground is often so hard and stony that a strong tool is necessary to dig it out; but the work entailed will be amply repaid if a perfect specimen be obtained and placed for observation in the aquarium.
Fig. 119.—Tube-building Worms: Terebella (left), Serpula (middle), Sabella (right)
The reader may possibly be acquainted with the tubes or cases that are constructed by the larvæ of caddis flies in fresh-water ponds and streams, and perhaps has noticed the ease with which these creatures may be made to construct new homes after having been turned out of doors. Similar experiments may be performed with Terebella; for when the worm has been extricated from its tube without injury—a work that requires great care on account of the soft and slender nature of the creature’s body—and placed in the aquarium with a bed of suitable material, it will build itself a new dwelling. As with the caddis larvæ, the different species may be known by the materials they select to construct their tubes, but in captivity they may be compelled to employ other than their favourite substance for this purpose. It is unfortunate, however, that Terebella is a nocturnal builder, and thus its movements are not so easily observed.
When removed from its tube its first movements suggest a resentment at the untimely ejection. This being over, it seeks a sheltered situation beneath the edge of a stone, and, at nightfall, commences the slow process of the construction of a fresh home. The particles of material at hand are seized by the tentacles, placed in position round the body, where they are held together by the sticky secretion already mentioned.
Fig. 120.—Terebella removed from its tube