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A fishlike creature (Amphioxus lanceolatus), two or three inches long, found in temperature seas; -- also called the lancelet. Its body is pointed at both ends. It is the lowest and most generalized of the vertebrates, having neither brain, skull, vertebræ, nor red blood. It forms the type of the group Acrania, Leptoca…

The lowest group of Vertebrata, including the amphioxus, in which no skull exists.

The lancelet. See Amphioxus.

group of vertebrates; -- so called from the cirri around the mouth; the Leptocardia. See Amphioxus.

er vertebrates generally, they are oval, and sometimes more or less spherical in form. In Amphioxus, and most invertebrates, the blood corpuscles are all white or colorless. -- White blood corpuscles (Physiol.), rounded, slightly flattened, nucleated cells, mainly protoplasmic in composition, and possessed of contract…

A cavity formed by the invagination of the outer wall of the body, as the atrium of an amphioxus and possibly the body cavity of vertebrates.

A small fishlike animal (Amphioxus lanceolatus), remarkable for the rudimentary condition of its organs. It is the type of the class Leptocardia. See Amphioxus, Leptocardia.

The lowest class of Vertebrata, including only the Amphioxus. The heart is represented only by a simple pulsating vessel. The blood is colorless; the brain, renal organs, and limbs are wanting, and the backbone is represented only by a simple, unsegmented notochord. See Amphioxus. [Written also Leptocardii.]…

One of the apertures of the gill of an ascidian, and of Amphioxus.

ll animals that have a backbone composed of bony or cartilaginous vertebræ, together with Amphioxus in which the backbone is represented by a simple undivided notochord. The Vertebrata always have a dorsal, or neural, cavity above the notochord or backbone, and a ventral, or visceral, cavity below it. The subdivisions…