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Diagram of a lancelet. The mouth is surrounded by a circle of tentacles; below the notochord is a row of gill slits; the vent is near the posterior (right) end below.

Lancelet

Diagram of a lancelet. The mouth is surrounded by a circle of tentacles; below the notochord is a row…

Lancelet fish (Branchiostoma) is sometimes called amphioxus, the type of the class Leptocardii, is a little creature, half and inch to four inches long. A lancelet may be regarded as a vertebrate reduced to its lowest terms. Instead of a jointed backbone, it has a cartilaginous notochord, running from the head to the tail. A nervous cord lies above it, enclosed in a membranous sheath. No skull is present and the nerve cord does not swell into a brain There are no eyes and no scles. The mouth is a vertical slit, without jaws. In this diagram we see the California lancelet twice the natural size, showing (g) gills, (l) liver, (m) mouth, (n) nerve cord, (nc) notochord.

Lancelet

Lancelet fish (Branchiostoma) is sometimes called amphioxus, the type of the class Leptocardii, is a…