CIRRHOPODA OCEAN LIFE "However distinct in outward appearance, and even in their internal economy, the creatures composing the primary divisions of animated nature may seem to be when superficially examined, closer investigation invariably reveals to the zoologist gradations of structure connecting most dissimilar types of organization, and leading so insensibly from one to another, that the precise bound ary-line which separates them is not always easily defined. The Cirrhopoda, indeed, present a strange combination of articulated limbs, united with many of the external characters of a Mollusk, as will be at once evident from the examination of any species of Bar nacle, whether Sesile or pedunculated." "At first sight no two objects can well be more unlike than a Barnacle and a Shrimp. The former is inclosed in a true shell composed of many pieces united either by shelly matter or by cartilage, which allow of the pro trusion and retraction of a hand of fine hairy filaments, the whole permanently affixed to foreign objects either by a thick, flexible stalk, or by a broad immovable base. The older naturalists as sociated these animals with the shell bearing MOLLUSCA, calling them multivalves, and even up to very recent times they have been considered as equally allied to the sub-kingdom just named and to that in which they occur here. Mr. Charles Darwin, however, in his admirable Monograph, has fully demonstrated the close affinity which subsists between them and the Crustacea, of which he, indeed, considers them only a sub-division. I pre fer, however, to treat them as a class by themselves, believing that the diversity between the groups is quite as great as that which subsists between the CRUSTACEA and the ARACHNIDA, or between the ARACHNIDA and the INSECTA. The Barnacle begins life in a form exactly like that of a young Entomostracous Crus taceau, with a; broad carapace, a single.eye, two pairs of antenna,• three pairs of jointed, branched, and ,Well-bristled legs, and a forked tail. It casts off its skin twice, undergoing, especially at . the second month, a considerable change of figure. At the third month it has assumed almost the form of . a Cypris or. Cythere, being inclosed in a bivalve shell, in which the front of the head with the antennae is greatly developed, equalling in bulk all the rest of the body. The single eye has become two, which are very large, and attached to the outer arms of two bent processes like the letters U U, which are seen within the thorax.
"In this stage the little animal searches about for some suitable spot for permanent residence; a ship's bottom, a piece of floating timber, the back of a whale or turtle, or the solid rock. When its selection is made, the two antennae, which project from the shell, pour out a glutinous gum or cement, which hardens in water, and firmly attaches them. Henceforth, the animal is a fixture, glued by the front of its head to its support. Another moult now takes place; the bivalve shell is thrown off, with the great eyes, and their u -like processes, and the little Cirriped is seen in its true form. It is now in effect a Stomapod Crustacean, attached by its antennae, the head greatly lengthened (in Lepas, &c.), the carapace composed of several pieces (valves), the legs modified into cirri, and made to execute their grasping movements backwards instead of forwards, and the whole abdomen obliter ated, or reduced to an inconspicuous rudiment.
"The sessile or stalkless Barnacles or Acorn-shells (Ballanid), appear to differ much in the formation of their shells from Lepadidx, (stalked,) but the diversity is produced by modification of the same essential valves. • " The food devoured by the Cirrhopoda would seem to consist of various minute animals, such as small Mollusks and micro scopic Crustacea, caught in the around them by a mechan-. ism at once simple and elegant. Any one who watches the movements of a living Cirrhopod will perceive that its arms, with their appended cirrhi, are in perpetual movement, being alter-, nately thrown out and retracted with great rapidity ; and that, when fully expanded, the plumose and flexible stems form an ex quisitely beautiful apparatus, admirably adapted to entangle.
any nutritious molecules, or minute living creatures, that may happen to be present in the circumscribed space over which this singular casting-net is thrown, and drag them down into the vicinity of the mouth, where, being seized by the jaws, they are . crushed and prepared for digestion. No sense but that of touch is required for the success of this singular mode of fishing ; and the delicacy with which the tentacula perceive the slightest con tact of a foreign body, shows that they are eminently sensible to tactile impressions."