Search the Dictionary

Any contractile vessel of invertebrates which is not of the nature of a real heart, especially one of those pertaining to the excretory system.

A posterior division of the stomach in some invertebrates.

An extensive artificial group of invertebrates, having all the parts arranged radially around the vertical axis of the body, and the various organs repeated symmetrically in each ray or spheromere.

That part of the eye of an invertebrate which corresponds in function with the retina of a vertebrate.

four united cells which occupy the axial part of the ocelli, or ommatidia, of the eyes of invertebrates, and contain the terminal nerve fibrillæ. See Illust. under Ommatidium.

One of the group of pigmented cells which surround the retinophoræ of invertebrates. See Illust. under Ommatidium.

One of the small scalelike structures covering parts of some invertebrates, as those on the wings of Lepidoptera and on the body of Thysanura; the elytra of certain annelids. See Lepidoptera.

e hard calcareous or chitinous external covering of mollusks, crustaceans, and some other invertebrates. In some mollusks, as the cuttlefishes, it is internal, or concealed by the mantle. Also, the hard covering of some vertebrates, as the armadillo, the tortoise, and the like.

The more or less firm or hardened framework of an invertebrate animal.

A small sac connected with the female reproductive organs of insects and many other invertebrates, serving to receive and retain the spermatozoa.

Any small calcareous or siliceous body found in the tissues of various invertebrate animals, especially in sponges and in most Alcyonaria.

An early or simple larval stage of trematode worms and some other invertebrates, which is capable or reproducing other germs by asexual generation; a nurse; a redia.

e special ganglion situated beneath the esophagus of arthropods, annelids, and some other invertebrates.

ion. -- Sucking stomach (Zoöl.), the muscular first stomach of certain insects and other invertebrates which suck liquid food.

ated process or organ, simple or branched, proceeding from the head or cephalic region of invertebrate animals, being either an organ of sense, prehension, or motion. Tentacle sheath (Zoöl.), a sheathlike structure around the base of the tentacles of many mollusks.

The external hard or firm covering of many invertebrate animals.

Invertebrate animals covered with shells, especially mollusks; shellfish.

Any hard calcareous or chitinous organ found in the mouth of various invertebrates and used in feeding or procuring food; as, the teeth of a mollusk or a starfish. In spite of the teeth, in defiance of opposition; in opposition to every effort. -- In the teeth, directly; in direct opposition; in front. "Nor strive wit…

A grand division of the animal kingdom, intermediate, in some respects, between the invertebrates and vertebrates, and by some writers united with the latter. They were formerly classed with acephalous mollusks. The body is usually covered with a firm external tunic, consisting in part of cellulose, and having two open…

ng, a system of organs which eliminate nitrogenous waste matter from the blood of certain invertebrates.