-CIRRHIPODA The genus Lepas of the Linnean system, after having oeen subdivided into different genera, has at length, by the efforts of M. Lamarck, been formed into a distinct class. The animals which it includes are protected by a cloak, strengthened by testaceous plates, to which the body adheres by one or more muscles. The head con sists of a slight eminence attached to the anterior por tion of the body, and, when in the natural position, near the inferior margin. The body is followed by a tail, supporting six feet on both sides, each of which consists of a short stem, which divides into two tapering jointed fringed filaments ; these, by their motion towards the mouth, bring the water and its contents within the sphere of that organ. The tail terminates in a conical tubular body, which has improperly been termed a proboscis.
The nervous system consists of a cord encircling the gullet, and giving out filaments to the mouth ; its two ends running along the belly and tail, and uniting at the base of each pair of feet to form a ganglion, and give off filaments.
The mouth is furnished with an obvious upper lip, a pair of maxilla: on each side, with the rudiments of palpi. Ellis says, " the mouth appears like that of a contracted purse, and is placed in front between the fore claws. In the folds of this membranous substance are six or eight horny laminx, or teeth, standing erect, each having a tendon proper to direct its own motion. Some of these teeth are serrated, others have tufts of sharp hairs instead of indentations on the convex side, that point down into the mouth ; so that no animalcule that becomes their prey can escape back." The gullet is very short, and enters into a stomach, having two cRca and glandular walls, which serve as a liver. The intes tine is short and simple, and terminates behind at the base of the caudal appendage. There are two salivary glands attached to the stomach. The gills are conical bodies, situated at the base of the feet. The organs of circulation are imperfectly understood. Poli observed the motion of the heart, but the vessels which are con nected with it are unknown.
The organs of reproduction appear, according to Cu vier, to consist of an ovarium giving out an oviduct, which traverses a body considered as a testicle, and both the canals unite in a common tube, which traverses the caudal appendage, and opens by a small pore at its ex tremity. This aperture Cuvier regards as simple, but
Ellis observes of the whole, " it is of a tubular figure, transparent, composed of rings lessening gradually to the extremity, where it is surrounded with a circle of small bristles, which likewise are moveable at the will of the animal. These, with other small hairs on the trunk, disappear when it dies." There is probably no union of individuals, each being perfect hermaphro dites.
The rapidity of growth which these animals exhibit is truly astonishing. A ship's bottom becomes covered with them in a few months, and the spawn of some kinds deposited on a feather, as stated in the memoirs of the \Vernerian Society, vol. ii. p. 243, will become unfolded, and attain maturity before the feather exhibits any symp toms of decay.
The animals of this class are all inhabitants of the sea, and are all fixed to other bodies. Many of them, how ever, are attached to floating wood, and others to the skin of marine animals, so that they enjoy all the advantagers of locomotion without the exercise of the exertion re quisite for its production. Their remains are seldom found in a fossil state. Some of the species have been used as food. In taking a view of the genera we shall distri bute them, as formerly, after the manner of Ellis, Phil. Trans. vol. 1. p. 848, into pedunculated and sessile.
The essential character of this order consists in the body being supported by a peduncle, the lower part of which is permanently fixed to other bodies.
The cloak consists of three membranes. The ex ternal one is the cuticle, and invests the whole external surface of the animal. Underneath this is the true skin, in which are formed the testaceous plates that protect the body. These plates or valves are evidently formed in the same manner as common shell, the layers of growth being indicated by the stria: on the surface. The inner membrane forms a sac for the body itself. This bag is closed on all sides except opposite to the tail, where there is a slit, through which the feet are pro truded.