The liver is of considerable size, of an orange-yellow colour, and of a soft and spongy texture. It gives rise to two hepatic ducts, which proceed to the extre mity of the spiral stomach, where they empty the orange-coloured bile which they contain by a common orifice.
The organs of circulation consist merely of veins and arteries, which we distinguish into pulmonic and sys temic. The veins, which have their origin in the feet, mouth, and annular cartilage, coalesce, and form two branches, which afterwards unite into a common trunk. This vessel, after descending through part of the vis cera into the abdomen, divides into two branches, each of which may be considered as a vena cava, conveying the blood to the lateral hearts. Each vena cava, at its origin, is joined by an equally large vessel, which emp ties its contents in a direction nearly at right angles with the former. These veins arise in the stomach, intestines, liver, and organs of generation. The vena cava receives a second large vessel, nearly in the same direction as the first, which has its origin in the tunic and the supports of the branchiez. From the size of the vena cava, in consequence of the union of these t two branches, and the appearance of muscular ridges on its inner surface, it has been compared by some to an auricle.
On each side, in the common cavity of the tunic, and near the gills, an aperture may be observed, the entrance to a bag or cavity. Each cavity is traversed by the vena cava of that side, and in its passage exhi bits a curious confirmation. The surface of the vein is covered with spongy glandular bodies of different shapes. These, upon being pressed, pour out an opake yellow mucous fluid. Within, these glands communicate by means of very wide ducts with the cavity of the vein. Indeed, when air is blown into the vein, it readily passes through the glands into the bag, and from thence into the cavity of the tunic ; and when air is blown into the bag, it likewise penetrates the gland, and passes through into the veins. The arteries with which these glands are furnished are comparatively minute.
It appears probable that these glands separate some principle from the blood, and that this is conveyed away by the ejection of the water from these venous bags into the common cavity. Were it practicable to
analyse the yellow mucus which these glands contain, some light might be thrown on this subject. Indeed, it appears not improbable that this arrangement is analo gous in its functions to the urinary system in the most perfect classes.
Each vena cava enters its corresponding lateral heart or ventricle, through an intervening valve. Each late ral heart is situated at the base of each gill, is pear shaped, black, moderately thick, with numerous pits on its inner surface. Its narrow end terminates without any valvular structure in the pulmonary artery. In the genus octopus, the lateral hearts are naked ; but in the generalolego and sepia, there is suspended from each, by a slender footstalk, a spongy round body, which is con cave beneath. The footstalk consists of fibres, which are attached to the surface of the heart, but there is no communication by ducts or vessels. The use of this organ is unknown.
The animals of this class continually reside in the water, and respire by means of gills or branchix. These are double, one on each side, corresponding with the lateral pulmonic ventricles. Each gill is connected at its opposite sides to the tunic, by means of fleshy ligamentous bands. Between these, the double leaves of the gills arc arranged in an alternate series. Each leaf is supported by a footstalk from the band, and is subdivided into smaller leaves, to expose a greater sur face to the water.
The pulmonary artery passes along this band, sends a branch into each footstalk, which, penetrating the substance of the gills, conveys the blood to its different divisions.
The systemic veins depart from the gills at the op posite extremity. These unite at the inferior band, and from each gill a vessel proceeds to the single cen tral or systemic heart or ventricle. In some of the ani mals of this class the systemic veins are somewhat en larged, and assume the appearance of auricles. The two pulmonary, or rather the systemic veins, enter the heart at the opposite side, each at the termination being furnished with a valvular organization.