. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 114 ANIMAL KINGDOM. face of the water in still warm evenings in tro- pical seas; some, as the clio borealis, figured above, abound in the Arctic seas. (See PTE- ROPODA.) 18. Cephalopoda, free cyclo-gangliated or mulluscous animals, with the feet disposed around the head, respiring by internal branchiae, and with the abdominal cavity enveloped by a muscular mantle open anteriorly. The cepha- lopods are all marine animals capable of swim- ming by means of membranous or muscular expansions, which are never supported by rays
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 114 ANIMAL KINGDOM. face of the water in still warm evenings in tro- pical seas; some, as the clio borealis, figured above, abound in the Arctic seas. (See PTE- ROPODA.) 18. Cephalopoda, free cyclo-gangliated or mulluscous animals, with the feet disposed around the head, respiring by internal branchiae, and with the abdominal cavity enveloped by a muscular mantle open anteriorly. The cepha- lopods are all marine animals capable of swim- ming by means of membranous or muscular expansions, which are never supported by rays. The surface of the body is often naked, some- times covered with a shell, which is generallypo- lythalamous, rarely monothalamous, and always inoperculate. There is often a concealed, loose, dorsal, calcareous or horny shell contained in a shut subcutaneous sac. The mouth is fur- nished with two horny or calcified mandibles, and the rudiments of an internal organized cartilaginous cranium and vertebral column are generally perceptible, together with some de- tached parts of the skeleton of vertebrata. The oesophagus is surrounded by a nervous collar, from which two supra-abdominal nervous co- lumns generally extend along the middle of the back, and sympathetic ganglia are observed in the abdominal cavity as in the inferior mollus- cous classes. These are predaceous animals, and the alimentary canal, though generally furnished with three enlargements, forming a crop, a gizzard, and a spiral or proper chylific stomach, is always very short. There are two pairs of salivary glands; the liver is of great size, and pours its secretion, with that of the pancreatic follicles, into the stomach, as in the inferior classes. There is always a strong mus- cular systemic ventricle, and generally a di- vided auricle placed at the beginning of the branchial arteries. The common form of the chylopoietic organs is seen in those of the loligopsis guttata, (Jig. 44,) where the liver (a a a «)
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