Page:The common shells of the sea-shore (IA commonshellsofse00wood 0).pdf/12

2 sometimes at one end of the body, and sometimes one at each end. They are not pretty, and they are not conspicuous; but they occur in great profusion, so that everyone who has used a trawl or a dredge, or has examined the shore at low-water, must have had his attention drawn towards them. Many species inhabit our coasts, and one or two of the most plentiful are figured in the illustration.

They have no head, and no limbs, and, as is often the case with marine animals, they pass through a kind of metamorphosis, so that their lowest form is as unlike their perfect shape as the caterpillar is unlike the butterfly. Sometimes they are separate animals, and sometimes they are attached to each other; while there are instances, such as the Salpæ, where they are single and combined in alternate generations.

The first example on our list is a creature well known to zoologists, and not unfamiliar to the seaside wanderer, provided that the latter can make use of his hands and eyes. Adhering to the heavy masses of sea-weed, fixed to stones and empty shells, or spread over the interior of rocky holes, may be seen certain gelatinous masses that are called by various popular names, such as sponges and sea-jellies. They are of various sizes and various colours. Some project boldly like sea-anemones, some are spread upon the supporting substance like jelly, and others are formed into regular patterns, mostly of a star or leaf shape. Some are olive green, some are orange, some yellow, and some of a bluish hue.

These curious objects belong to the great group of Tunicata, and are called, from the Greek word Ascos, which signifies a pouch made of skin. They furthermore belong to that family of the group which is called Botryllidæ, or Grape-animals, because they consist of a number of individuals connected together like grapes upon a bunch.

Of these, one of the best known and most typical