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A joint of the cirri of the Crinoidea; a joint or segment of an arthropod appendage.

Divided into two lobes or segments.

A small, clear space in the segments of the ovum, the precursor of the nucleus.

The cavity of the blastosphere, or segmentation cavity.

One of the segments first formed by the division of the ovum. Balfour.

The upper arm; the segment of the fore limb between the shoulder and the elbow.

the central cavities, or ventricles, and the walls thicken unequally and become the three segments, the fore-, mid-, and hind-brain.

Furnished with branchiæ; as, branchiate segments.

The state of being made up of branchiate segments. R. Wiedersheim.

The anterior segment of the shell of trilobites.

A segment forming a side piece in the head of a cask. Knight.

Having the lowest inferior segment of a pinna nearer the rachis than the lowest superior one; -- said of a mode of branching in ferns, and opposed to anadromous.

Having the food yolk placed at the center of the ovum, segmentation being either regular or unequal. Balfour.

he body is flattened, and usually but not always long, and composed of numerous joints or segments, each of which may contain a complete set of male and female reproductive organs. They have neither mouth nor intestine. See Tapeworm. [Written also Cestoda.]

Annelida, characterized by the presence of lateral setæ, or spines, on most or all of the segments. They are divided into two principal groups: Oligochæta, including the earthworms and allied forms, and Polychæta, including most of the marine species.

One of the two principal orders of myriapods. They have numerous segments, each bearing two pairs of small, slender legs, which are attached ventrallly, near together.

uding the centipeds. They have a single pair of elongated legs attached laterally to each segment; well developed jaws; and a pair of thoracic legs converted into poison fangs. They are insectivorous, very active, and some species grow to the length of a foot.

The yellowish green pigment in the inner segment of the cones of the retina. See Chromophane.

ral name for the several coloring matters, red, green, yellow, etc., present in the inner segments in the cones of the retina, held in solution by fats, and slowly decolorized by light; distinct from the photochemical pigments of the rods of the retina.

odia of Annelida. Those near the head of annelids are Tentacular cirri; those of the last segment are caudal cirri.