(After Allman.) sensory, contractile and pro tective in function.
(3) Contractile r?i-?
Iwanzov  has brought forward strong grounds for the latter view, pointing out that the cnidoblast has no contractile mechanism and that measurements show discharged capsules to be on the average slightly larger than undischarged ones.
The muscular tissue consists primarily of processes from the bases of the epithelial cells, processes which are contractile in nature and may be distinctly striated.
A further stage in evolution is that the muscle-cells lose their connexion with the epithelium and come to lie entirely beneath it, forming a sub-epithelial contractile layer, developed chiefly in the tentacles of the polyp. The of the evolution of the ganglioncells is probably similar; an epithelial cell develops processes of nervous nature from the base, which come into connexion with the bases of the sensory cells, with the muscular cells, and with the similar processes of other nerve-cells; next the nerve-cell loses its connexion with the outer epithelium and becomes a sub-epithelial ganglion-cell which is closely connected with the muscular layer, conveying stimuli from the sensory cells to the contractile elements.
6), from the bases of which arise contractile muscular processes lying in the plane of the transverse section of the body.
In addition to tentacles, there may be marginal cirri (Laodice) with a solid endodermal axis, spirally coiled, very contractile, and bearing a terminal battery of nematocysts.
68, k), absent in Chondrophorida and Cystophorida; they are contractile and resemble, both in appearance, structure and function, the umbrella of a medusa, with radial canals, ring-canal and velum; but they are without manubrium, tentacles or sense-organs, and are always bilaterally symmetrical, a peculiarity of form related with the fact that they are attached on one side to the stem.
These two vessels in the Oligochaeta are united in the anterior region of the body by a smaller or greater number of branches which surround the oesophagus and are, some of them at least, contractile and in that case wider than the rest.
Several specially large contractile trunks in the anterior segments uniting the dorsal and ventral vessels.
In Hirudo and the Gnathobdellidae there is only one system of cavities which consist of four principal longitudinal trunks, of which the two lateral are contractile, which communicate with a network ramifying everywhere, even among the cells of the epidermis.
In the veliger stage many Pectinibranchia (Purpura, Nassa, &c.) exhibit, in the dorsal region behind the head, a contractile area of the body-wall.
Similar rhythmically contractile shell of Rostellaria rectirostris.
Kn, Contractile sinus.
(Original.) convert it into a lung-sac with a small contractile aperture, belong to stages in the development later than any represented in our figures.
The head bears a single pair of contractile but not invaginable tentacles, at the base of which are the eyes.
The dorsal vessel is an elongate tube, Oblique tergal whose abdominal portion is usually c ha m b e r e d, forming a contractile heartfi Io the (g io).) At th ' constrictions between the pericardium l?': ?:' chambers are paired slits, through which the blood passes from the surround Tergo-sternal .
The blood, which is a non-corpuscular fluid, is propelled forwards by the contractile dorsal vessel and collected into the central bloodsinus; this lies over the stomochord, and is surrounded on three sides by a closed vesicle, with contractile walls, called the pericardium (Herzblase).
It consists of a definite contractile sac or sacs lying on the dorsal side of the alimentary canal near the oesophagus, and in preparations of Terebratulina made by quickly removing the viscera and examining them in sea-water under a microscope, he was able to count the pulsations, which followed one another at intervals of 30-40 seconds.
The great dorsal contractile vessel or " heart " of Limulus is closely similar to that of Scorpio; its ostia or incurrent orifices are FIG.
Ehrenberg), a genus of lobose Rhizopoda, characterized by a chitinous plano-convex shell, the circular aperture central on the fiat ventral face, and more than one nucleus and contractile vacuole.
The tentacles serve for the capture of prey and are very contractile, being often protruded to a great length or, on the other hand, retracted and forming corkscrew-like curls.
A pair of coiled nephridial tubes (n) formed of a file of perforated `' drain-pipe "cells, with ciliated tag-like" flame "cells (f), open into a contractile bladder (bl), FIG.
3, b, d) the cingulum is a mere - contractile hood.
(iv.) Trophi uncinate: Flosculariaceae; disk a contractile cup, often lobed, the cingulum of long vibratile cilia, of very long motionless bristles or absent, rarely with an outer zone of fine cilia.
A dorsal contractile heart, with symmetrical right and left auricles receiving aerated blood from the ctenidia and mantle skirt, is present, being unequally developed only in those few forms which are inequivalve.
That substance, in small doses, favours the contractile power of muscle.
The drug appears to have no influence upon the contractile cells that constitute muscle-fibre, any more than it has directly upon the secretory cells that constitute any gland.
A reddish-brown body, known as the eyespot, is usually situated near the limits of the hyaline portion, and in the protoplasm contractile vacuoles similar to those of lower animals have been occasionally detected.
The primary and secondary bars which separate and divide the successive gill-clefts from one another are traversed by blood-vessels which run from a simple tubular contractile ventral branchial vessel along the bars into a dorsal aorta.
The muscle-bands are very contractile, rendering the scyphistoma one of the most difficult of all organisms to preserve in an expanded condition.
These captacula are of unequal length, highly contractile and extensile, easily thrown off and regenerated.
The roof of the mouth is formed by the palate, terminating behind by a muscular, contractile arch, having in man and a few other species a median projection called the uvula, beneath which the mouth communicates with the pharynx.