Ventral Sentence Examples

The right ventricle occupies the ventral portion of the heart.

In the latter, the segmentally arranged ganglia are more sharply marked off from the connectives than in other Chaetopods, where nerve cells exist along the whole ventral chain, though more numerous in segmentally disposed swellings.

The principal trunks consist of a dorsal vessel lying above the gut, and a ventral vessel below the gut but above the nervous cord.

The dorsal vessel also communicates with the ventral vessel indirectly by the intestinal sinus, which gives off branches to both the longitudinal trunks, and by tegementary vessels and capillaries which supply the skin and the nephridia.

In the smaller and simpler forms the capillary networks are much reduced, but the dorsal and ventral vessels are usually present.

In this worm the ventral blood-vessel is so swollen as to occupy nearly the whole of the available coelom.

Setae always present and often very large, much varied in form and very numerous, borne by the dorsal and ventral parapodia (when present).

The prostomium bears often processes, both dorsal and ventral, which in the Sabellids are split into the circle of branchial plumes, which surround or nearly surround the mouth in those tube-dwelling Annelids.

Tomopteris is remarkable for the fact that the hammer-shaped prostomium has paired ventral processes each with a single seta.

In these forms the bundles of setae are either capilliform or uncinate, and the dorsal setae of the thorax are like the ventral setae of the abdomen.

Appendages of body re „ duced to branchiae, present only in four species, and - - to the ventral copulatory 32 appendages of Alma and Criodrilus.

Several specially large contractile trunks in the anterior segments uniting the dorsal and ventral vessels.

The vascular system is simple with as a rule direct communication between dorsal and ventral vessels in each segment.

Vascular system complicated without regular connexion between dorsal and ventral vessels, except in anterior segments.

There are two chitinous jaws in the buccal cavity, a dorsal and a ventral, which are of specially complicated structure in Cirrodrilus.

The median lacuna no longer exists, but is represented by a dorsal and ventral sinus.

Ventral view to show legs and somites.

The mouth is ventral, the otolith dorsal.

All the fins have a rounded outline; the short dorsal fin is without a spine, but the males possess a very thick and flattened outer ray in the ventral fins.

On the other hand, in certain Polychaeta the bundles of setae are so extensive that they nearly form a complete circle surrounding the body; and in the Oligochaet genus Perichaeta (=Pheretima), and some allies, there is actually a complete circle of setae in each segment broken only by minute gaps, one dorsal, the other ventral.

The former lodges the dorsal, the latter the ventral, bloodvessel.

In favour of regarding the vascular system as totally absent, is the fact that the median coelomic channels contain no dorsal and ventral vessel.

The first is a ventral flexure in the antero-posterior or sagittal plane; the result of this is to approximate the two ends of the alimentary canal.

But ultimately the coil becomes ventral or endogastric, in consequence of the second torsion movement then apparent.

The most important of these opens by the ventral pedal pore, situated in the median line in the anterior half of the foot.

Shell conical; foot secreting a ventral calcareous plate; animal fixed.

Thus the base of the gill passes in a slanting direction across the right-hand side of the kidney, the posterior end being dorsal to the apex of the gland, and the anterior end ventral to the right-hand corner.

Adult without shell; a sub-epithelial pseudoconch formed by connective tissue; pallial cavity ventral.

Shell not coiled, symmetrical; pallial cavity ventral.

The next six families include the animals formerly known as Gymnosomatous Pteropods, characterized by the absence of mantle and shell, the reduction of the ventral surface of the foot, and the parapodial fins at the anterior end of the body.

The thoracic segments, as seen in an early stage of the ventral plate, display in a well-marked manner the essential elements of the insect segment.

They are developed on the ventral surface of the body and are six in number, one pair arising from the eighth ventral plate and two pairs from the ninth.

The continuous layer of cells from which the nervous system is developed undergoes a segmentation analogous with that we have described as occurring in the ventral plate; there is thus formed a pair of contiguous ganglia for each segment of the body, but there is no ganglion for the telson.

There are other ganglia in addition to those of the ventral chain, and Janet supposes that the ganglia of the sympathetic system indicate the existence of three anterior head-segments; the remains of the segments themselves are, in accordance with this view, to be sought in the XIII.

The germ band evidently marks the ventral aspect of the developing insect, whose body must be completed by the extension of the embryo so as to enclose the yolk dorsally.

The ventral is immediately below the second dorsal, and is also followed by finlets.

This is brought about by a double commissure, of which the ventral portion is considerably thicker than the dorsal, and which, together with the brain-lobes, constitutes a ring through which both proboscis and proboscidian sheath pass.

The brain-lobes are generally four in number, a ventral and a dorsal pair, respectively united together by the above-mentioned commissures, and moreover anteriorly interfusing with each other, right and left.

In Carinella this separation into lobes of the anterior thickenings of the cords has not yet commenced, the ventral commissure at the same time being extremely bulky.

In others there is an approximation of the lateral stems towards the median ventral line (Drepanophorus); in a genus of Heteronemertines (Langia), on the other hand, an arrangement occurs by which the longitudinal stems are no longer lateral, but have more or less approached each other dorsally.

In the Metanemertini there is a curious diverticulum of the intestine which stretches forward in the median line, ventral to the socalled stomach.

The median dorsal vessel, however, remains distinct, but instead of continuing its course beneath the proboscidian sheath it is first enclosed by the ventral musculature of this organ, and still farther forwards it even bulges out longitudinally into the cavity of the sheath.

The two external openings of the nephridia are situated sometimes more 2 towards the ventral, at other times more towards the dorsal side.

The nervous system, composed of a ring and a ventral cord, retains its primitive connexion with the ectoderm.

In the neck of the proboscis the fibrous layer is greatly thickened, and other intensifications of this layer occur in the dorsal and ventral middle lines of the trunk extending to the posterior end of the body.

The dorsal epidermal nerve-tract is continued in front into the ventral wall of the collar nerve-tube, and at the point of junction there is a circular commissural thickening following the posterior rim of the collar and affording a special connexion between the dorsal and ventral nervetracts.

From the ventral surface of the collar nerve-tube numerous motor fibres may be seen passing to the subjacent musculature.

By the pulsation of the pericardial vesicle (best observed in the larva) the blood is driven into the glomerulus, from which it issues by efferent vessels which effect a junction with the ventral (sub-intestinal) vessel in the trunk.

The valves are also in some species very unequal in their respective thickness, as may be seen in Productus (Daviesiella) 1 llangollensis, Davidsonia verneuilii, &c., and while the space allotted to the animal is very great in many species, as in Terebratula sphaeroidalis, it is very small in others belonging to Stro phomena, Leptaena, Chonetes, &c. The ventral valve is usually the thickest, and in some forms is six or seven times as great as the opposite one.

The valves are distinguished as dorsal and ventral.

The ventral valve is usually the larger, and in many genera, such as Terebratula and Rhynchonella, has a prominent beak or umbo, with a circular or otherwise shaped foramen at or near its extremity, partly bounded by one or two plates, termed a deltidium.

The ventral valve in many of the genera is provided with two curved hinge-teeth, which fit into corresponding sockets in the opposite valve, so that the valves cannot be separated without breaking one of the teeth.

In the region of the mouth where the two halves of the small arm-sinus approach one another they open into a central sinus lying beneath the oesophagus and partly walled in by the two halves of the ventral mesentery.

The stalk is an extension of the ventral body-wall, and contains a portion of the coelom which, in Discinisca and Lingula, remains in communication with the general body cavity.

The intestine is slung by a median dorsal and ventral mesentery which divides the body cavity into two symmetrically shaped halves; it is " stayed " by two transverse septa, the anterior or gastroparietal band running from the stomach to the body wall and the posterior or ileoparietal band running from the intestine to the body wall.

The heart gives off posteriorly a second median vessel which divides almost at once into a right and a left half, each of which again divides into two vessels which run to the dorsal and ventral mantles respectively.

The dorsal branch sends a blind twig into each of the diverticula of the dorsal mantle-sinus, the ventral branch supplies the nephridia and neighbouring parts before reaching the ventral lobe of the mantle.

Both dorsal and ventral branches supply the generative organs.

The divaricators proper are stated by Hancock to arise from the ventral valve, one on each side, a little in advance of and close to the adductors, and after rapidly diminishing in size become attached to the cardinal process, a space or prominence between the sockets in the dorsal valve.

The accessory divaricators are, according to the same authority, a pair of small muscles which have their ends attached to the ventral valve, one on each side of the median line, a little behind the united basis of the adductors, and again to the extreme point of the cardinal process.

The dorsal adjustors are fixed to the ventral surface of the peduncle, and are again inserted into the hinge-plate in the smaller valve.

The ventral adjustors are considered to pass from the inner extremity M FIG.

Laterally, the sub-oesophageal ganglia give off (v.) nerves to the ventral mantle, and finally they supply (vi.) branches to the various muscles.

There are four of such masses, two dorsal and two ventral, and as a rule they extend between 1.

The nerves running to the dorsal parts are white, with black edges; those running to the ventral parts are solid black.

These plates are secreted by the ventral lobe of the mantle, and were named by von Buch in 1834 the " deltidium."

It subsequently becomes attached to the ventral valve, and develops into the pseudodeltidium, in the Neotremata and the Protremata.

The pedicle passes out at right angles to the plane of junction of the valves of the shell; the opening is confined to the ventral valve, and may take the form of a slit, or may be closed by the development of a special plate called the listrium, or by a pseudo-deltidium.

The pro-deltidium originating on the dorsal surface later becomes anchylosed with the ventral valve.

The ovary is double, and the oviducts open by a median ventral pore about the middle of the body; in this region there is a second swelling.

In each somite of the mesosoma is a small, free entosternite having a similar position, but below or ventral to the nerve cords, and having a smaller number of muscles attached to it.

It became isolated and detached, why or with what advantage to the organism it is difficult to say, and at that period of Arachnidan development the great ventral nerve cords occupied a more lateral position than they do at present.

The supra-pectinal entosternite lies ventral to the nerve cords.

Their movement in an upward or downward direction in Limulus and Mygale must exert a pumping action on the blood contained in the dorsal arteries and the ventral veins respectively.

It seems that there is a primitive tendency in the Arthropoda for the arteries to accompany the nerve cords, and a " supra-spinal " artery - that is to say, an artery in close relation to the ventral nerve cords--has been described in several cases.

The blood is brought to the respiratory organs in both cases by a great venous collecting sinus having a ventral median position.

In both animals the wall of the pericardial sinus is connected by vertical muscular bands to the wall of the ventral venous sinus (its lateral expansions around the lung-books in Scorpio) in each somite through which the pericardium passes.

Whether the pericardium and the ventral sinus are made to expand simultaneously or all the movement is made by one only of the surfaces concerned, must depend on conditions of tension.

Scorpions copulate with the ventral surfaces in contact.

Ventral view of a female with the appendages cut short near the base.

Ventral view with the prosomatic appendages cut short excepting the chelicerae (I) whose sharp retroverts are seen.

Its ventral surface provided with one prosternal, two mesosternal and one metasternal plate.

A, Ventral view of prosoma and of anterior region of opistho soma with the appendages cut off near the base; a and b, B, Dorsal view.

Respiratory organs tracheal, opening upon the ventral surface of the 2nd and 3rd, and sometimes also of the 4th somite of the opisthosoma.

Ventral view with the appendages cut off at the base.

Appendages of the 3rd, 4th, 5th and 6th pairs similar in form and function, tipped with two claws, their basal segments in contact in the median ventral line.

A movable membranous j oint between the prosoma and the opisthosoma, the generative aperture opening upon the ventral side of the membrane.

A, Lateral view with appendages III to VI removed; 1, plate covering the whole dorsal area, representing the fused tergal sclerites of the prosoma and opisthosoma; 2, similarly-formed ventral plate; 3, tracheal stigma.

Ventral fins below or in front of the pectorals, the pelvic bones posterior to the clavicular symphysis and only loosely attached to it by ligament.

Outline of the ventral surface to show the external apertures and nervous system; a, rosette-organ; b, uterine pore; c, terminal sucker; e, vaginal pore; g, male gonopore; n, o, p, nervous system.

The former bears two terminal suckers on the flattened dorsal and ventral surfaces, the latter six hooks near the tip of the tail.

In them a ventral surface containing the usually median male and female genital apertures is generally distinguishable from the smooth FIG.

In such cases the male organs are regarded as indicating the dorsal surface, the female organs as belonging to the ventral surface.

The ventral surface is characterized by one or more suckers and apertures.

The chief genital pore is placed anteriorly between the oral sucker and the ventral one, and is posterior only in Holostomidae, Gasterostomidae and a few Distomidae.

A, Fasciola hepatica, from the ventral surface (X 2); the alimentary and nervous systems only shown on the left side of the figure, the excretory only on the right; a, right main branch of the intestine; c, a diverticulum; g, lateral ganglion; n, lateral nerve; o, mouth; p, pharynx; s, ventral sucker; cs, cirrus sac; d, left anterior dorsal excretory vessel; m, main vessel; v, left anterior ventral trunk; x, excretory pore.

A, Dorsal view showing the nervous system and digestive system; a, mouth; b, pharynx; c, d, e, gut; E, post-genital union of two limbs of gut; f, excretory pore; g, vaginal pore; h, j, k, brain and nerves; 1, dorsal nerves; m, ventral nerves; n, adoral sucker; o, posterior sucker; p, hooks on posterior sucker; r, vitello-intestinal duct.

B, Ventral view showing the The further history of the animal is only known in a few cases.

If successful, the larva throws off its cilia and develops a dorsal papilla, a median ventral sucker and an additional pair of lateral suckers.

It is terminated by a well-developed structure (fg) corresponding with the apical sense-organ of ordinary Trochospheres, and an excretory organ (nph) of the type familiar in these larvae occurs on the ventral side of the stomach.

Their body is cylindrical, flexible in every part, covered with smooth or keeled scales, and provided with broad ventral and subcaudal scutes.

Their body is generally compressed and slender; their broad ventral scutes are often carinate on the sides.

Their body is covered with small scales and the ventral scutes are mostly narrow; the tail tapering; head flat, rather short; and the eyes of small size.

The scales of the long, cylindrical body are smooth and small, scarcely enlarged on the ventral side.

Internal, skeletal characters, useless for ordinary practical purposes, are the various apophyses on the ventral side of the vertebrae and the penial armaments fancied by Cope.

Acrochordus javanicus has no enlarged ventral shields; the flat, viperish-looking head is covered with small granules, with the eyes and nostrils well on the upper surface.

Chersydrus ranges from Madras to New Guinea; the body and tail are laterally compressed and form a ventral fold which is covered with tiny scales like the rest of the body.

Another variety has a red back, with pairs of black crossbars, the bands of each pair being separated by a narrow yellow space; sides brown, dotted with black; belly dark green, the outer portion of each ventral shield being yellow,.

In this division the ovipositor issues from the ventral surface of the abdomen; the pronotum reaches back to the tegulae;.

By means of the oar-like hindlegs they swim actively through the water with the ventral surface upwards; the fore-legs are inserted at the hinder edge of the prosternum.

These last characteristics also separate them essentially from the Pycnogonida, some members of which resemble them to a certain extent in having only four pairs of limbs, no gnathites, no respiratory organs, a ganglionated ventral nervous system, and the abdomen reduced to a mere rudiment projecting between the last pair of legs.

It consists in attaching to the loop or ventral segment of a vibrating body, e.g.

The vibrations of the larger mass are communicated to the thread, which by proper adjustment of its length and tension vibrates in unison and divides itself into one or more loops or ventral segments easily discernible by a spectator.

If the length of the thread be k"pt invariable, a certain tension will give but one ventral segment; the fundamental note of the thread is then of the same pitch as the note of the body to which it is attached.

In like manner, on further lowering the tension to one ninth, three ventral segments will be formed, and so on.

The law that, caeteris paribus, n varies inversely as the thickness may be tested by forming a string of four lengths of the single thread used before, and consequently of double the thickness of the latter, when, for the same length and tension, the compound thread will exhibit double the number of ventral segments presented by the single thread.

The plate is then bowed at the edge and is thrown into vibration between nodal lines or curves and the sand is thrown from the moving parts or ventral segments into these lines, forming " Chladni's figures."

As in the case of a musical string, so here we find that the pitch of the note is higher for a given plate the greater the number of ventral segments into which it is divided; but the converse of this does not hold good, two different notes being obtainable with the same number of such segments, the position of the nodal lines being, however, different.

If the plate be small, it is sufficient, in order to bring out the simpler sand-figures, to hold the plate firmly between two fingers of the same hand placed at any point where at least two nodal lines meet, for instance the centre in (1) and (2), and to draw a violin bow downwards across the edge near the middle of a ventral segment.

In particular the Schizopods of the family Mysidae, which are abundant in the sea round our coasts, are often called "Opossumshrimps" from the fact that the female is provided with a ventral pouch or "marsupium" in which the eggs and young are carried.

In 1892 he distinguished the former as those in which the first antennae of the male have both members modified for holding the female, and the genital openings of the female have a ventral position, sometimes in close proximity, sometimes strongly lateral; the latter as those in which the first antennae of the male are similar to those of the female, the function of holding her being transferred to the male maxillipeds, while the genital openings of the female are dorsal, though at times strongly lateral.

The shell is developed on the dorsal surface behind the velum, the foot on the opposite or ventral surface behind the mouth.

Procoelous vertebrae; ventral portions of the clavicles not dilated; parietal bones fused into one.

H, enlarged view of the median ventral appendage.

They are six in number, median, ventral and dorsal, and two unequal lateral pairs.

The ventral fins are slightly anterior to the origin of the dorsal fin; and the spine consists of from fortyseven to forty-nine vertebrae.

For many years only the dorsal surface of Trilobites was known, nothing having been ascertained of the ventral surface and appendages.

Comparatively recently, however, specimens have been obtained with the ventral surface exposed, revealing the number and structure of the limbs.

A pair of the latter was articulated to the sides of a moderately wide dorsal plate on each segment of the body, and similar limbs were attached to the ventral surface of the head-shield behind the mouth.

It will be seen that the umbilical fissure (u) divides the organ into right and left halves, as in the lower vertebrates, but that the ventral part of each half is divided into a central and lateral lobe.

The mantle-skirt is always long, and hides the rest of the animal from view, its dependent margins meeting in the middle line below the ventral surface when the animal is retracted; it is, as it were, slit in the median line before and behind so as to form two flaps, a right and a left; on these the right and the left calcareous valves of the shell are borne respectively, connected by an uncalcified part of the shell called the ligament.

When the edges of the mantle ventral to the inhalant orifice are united, an anterior aperture is left for the protrusion of the foot, and thus there are three pallial apertures altogether, and species in this condition are called " Tripora."

In them the foot has a flat ventral surface used for creeping, as in Gastropods, the byssus gland is but slightly developed, the pleural ganglia are distinct, there is a relic of the pharyngeal cavity, in some forms with a pair of glandular sacs, the gonads retain their primitive connexion with the renal cavities, and the otocysts are open.

Trigoniidae.-Shell thick; foot elongated, pointed in front and behind, ventral border sharp; byssus absent.

As a result, the Coelomata, and with them the Mollusca, present (in the first instance) the general condition of body known as bilateral symmetry; the dorsal is differentiated from the ventral surface, whilst a right and a left side similar to, or rather the complements of, one another are permanently established.

It corresponds to the ventral part of the body-wall in other animals.

The ventral cords are the pedal, the dorso-lateral, the pleural, the former innervating the foot, the latter the mantle.

The dorsal half of the collar is the cerebral commissure, the ventral the labial commissure.

The Prorhipidoglossomorpha are distinguished by the separation of the genital coelom from the pericardium, and by the long visceral commissure passing ventral to the intestine.

The mouth, a longitudinal slit, opens on to the ventral surface of the head.

The nervous system consists of a cerebral ganglion in the head, a conspicuous ventral ganglion in the trunk, and of lateral cornmissures uniting these ganglia on each side.

These were investigated by Tulasne in 1853, who gave them the name spermogonia The lower, ventral portion of the sperm09' gonium is lined by delicate hyphae, the sterigmata, which give origin to minute colourless cells, the spermatia.

The ventral surface forms a flat creeping "foot," and between mantle and foot is a pallial groove in which there is on each side a series of gills.

The mouth leads into the buccal cavity, on the ventral side of which opens the radular caecum.

A small longitudinal projection in the ventral groove represents the A, Lateral view.

Into the pharyngeal cavity open salivary glands and radular sac. The former are paired and ventral, and open on a subradular prominence.

The mouth is anterior, terminal and crescentic, and beneath it is a rounded ventral shield.

The latter extends backwards on the ventral side of the intestine.

Polygordius and Protodrilus live in sand, but while the former moves by means of the contraction of its body-wall muscles, Protodrilus can progress by the action of the bands of cilia surrounding its segments, and of the longitudinal ciliated ventral groove.

The body is composed of a large number of segments; the prostomium bears a pair of tentacles; the nervous system consists of a brain and longitudinal ventral nerve cords closely connected with the epidermis (without distinct ganglia), widely separated in Saccocirrus, closely approximated in Protodrilus, fused together in Polygordius; the coelom is well developed, the septa are distinct, and the dorsal and ventral longitudinal mesenteries are complete; the nephridia are simple, and open into the coelom.

It resembles Dinophilus in the possession of a ventral pharyngeal pouch (which bears teeth in Histriodrilus only), the small number of segments, and absence of distinct septa, the absence of a vascular system, the presence of distinct ganglia on the ventral nerve cords, and of small nephridia which do not appear to open internally.

There is a welldeveloped brain dorsal, to the mouth; this gives off a pair of oesophageal commissures, which surround the oesophagus and unite in a median ventral nerve-cord which runs between the longitudinal muscles to the posterior end of the body.

There are no distinct ganglia, but ganglion cells are uniformly distributed along the ventral side of the cord.

Strands breaking up the f, Ventral nerve-cord.

The thallus is somewhat spherical and unicellular, exhibiting a distinction between anterior and posterior extremities, and dorsal and ventral surfaces.

This is the carpogonium; it consists of a ventral portion which contains a nucleus, but in which no oosphere is differentiated, and an elongated tubular portion known as the trichogyne, into which the cytoplasm extends.

The ventral portion of the carpogonium may be imbedded deep in the thallus in the massive species; the trichogyne, however, always reaches the surface.

There is a single unsegmented nerve-cord which runs along the ventral middle line and enlarges posteriorly into a caudal ganglion and anteriorly in a ganglion, the brain, which is not supra-oesophageal.

The order is divided into five tribes by characters based on differences in position of the ovules - which are generally semianatropous so that the seed is peltate with the hilum in the centre on one side (or ventral), but sometimes, as in Hottonia and (From Strasburger's Lehrbuch der Botanik.) FIG.

In our well-known hive-bee (Apis) and humble-bees (Bombus) the wax glands are ventral FIG.

By a horizontal incision on each side of the body a large ventral area has been separated and turned over, as it were on a hinge, to the animal's left side.

The atrial region extends from the mouth over about twothirds of the length of the body, terminating at a large median ventral aperture, the atriopore; this is the excurrent orifice for the respiratory current of water and also serves for the evacuation of the generative products.

The ventral side of the body in the atrial region is broad and convex, so that the body presents the appearance of a spherical triangle in transverse section, the apex being formed by the dorsal fin and the angles bordered by two hollow folds, the metapleural folds, each of which contains a continuous longitudinal lymph-space, the metapleural canal.

It is characterized by the presence of a special development of the lophioderm or median fin-system, namely, the ventral fin, which is composed of two portions, a lower keel-like portion, which underlies an upper chambered portion, each chamber containing typically a pair of gelatinous fin rays.

Each primary gill-cleft becomes divided into two by a tongue-bar which grows down secondarily from the upper wall of the cleft and fuses with the ventral wall.

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 ventral branchial vessel lies below the hypobranchial groove or endostyle, and is the representative of a heart.

In the same region of the body, namely, close behind the pharynx, a large diverticulum is given off from the ventral side of the gut.

Corresponding with each pair of myotomes, and subject to the same alternation, two pairs of spinal nerves arise from the neurochord, namely, a right and left pair of compact dorsal sensory roots without ganglionic enlargement, and a right and left pair of ventral motor roots composed of loose fibres issuing separately from the neurochord and passing directly to their termination on the muscle-plates of the myotomes.

The ventral roots, on the contrary, are myal or segmental in position.

The first of these usually carries a ventral tube, furnished with paired eversible sacs which assist the insects in walking on smooth surfaces, and perhaps serve also as organs for breathing.

Willem it appears that the viscid fluid which causes the adherence of the ventral tube is secreted by a pair of glands in the head whose ducts open into a superficial groove leading from the second maxillae backward to the tube on the first abdominal segment.

Female, ventral view, magnified three times.

There is a strongly marked median longitudinal ventral black stripe, to which the lower ends of the transverse side stripes are usually united, but the dorsal stripe (also strongly marked) is completely isolated in its posterior half, and the uppermost of the broad haunch stripes runs nearly parallel to it.

The muscular projection of the ventral surface called the foot, whose various modifications characterize the different classes of Mollusca, is almost entirely aborted.

In its simplest form the exoskeleton of a typical somite is a ring of chitin defined from the rings in front and behind by areas of thinner integument forming moveable joints, and having a pair of appendages articulated to its ventral surface on either side of the middle line.

A dorsal and a ventral plate are often distinguished, known respectively as the tergum and the sternum, and the tergum may overhang the insertion of the limb on each side as a free plate called the pleuron.

The central nervous system is constructed on the same general plan as in the other Arthropoda, consisting of a supra-oesophageal ganglionic mass or brain, united by circumoesophageal connectives with a double ventral chain of segmentally arranged ganglia.

In the primitive Phyllopoda the ventral chain retains the ladder-like arrangement found in some Annelids and lower worms, the two halves being widely separated and the pairs of ganglia connected together across the middle line by double transverse commissures.

In the higher groups the two halves of the chain are more or less closely approximated and coalesced, and, in addition, a concentration of the ganglia in a longitudinal direction takes place, leading ultimately, in many cases, to the formation of an unsegmented ganglionic mass representing the whole of the ventral chain.

The appendages posterior to the mandibles appear as buds on the ventral surface of the somites, and in the most primitive cases they become differentiated, like the somites which bear them, in regular order from before backwards.

The edge of the mantle at the anterior aperture is very thick and muscular; at the posterior aperture also there is a circular muscle, and here the edge is interrupted by a ventral sinus and is provided internally with a dorsal and ventral valve which can be applied to each other so as to close the aperture.

This buccal sac is provided with a dorsal mandible and a ventral radula.

The buccal cavity contains a sense-organ on the ventral side called the sub-radular organ.

The gastrula thus formed has a large blastopore, which is at first posterior but afterwards gradually moves towards the anterior end of the ventral surface.

The shell-gland is formed on the dorsal surface, and the mantle arises as two lateral lobes which afterwards unite by their ventral edges to form the tubular mantle of the adult.

The foot arises as a prominence on the ventral surface and grows forward, and at the end of five or six days the velum atrophies and the foot becomes the organ of locomotion; the animal then ceases to swim and sinks to the bottom.

The mouth and cloacal aperture are generally at opposite ends of the ventral surface.

The embryology of Myzostoma has been C A, Ventral view of Myzostoma.

Dorsal and ventral aspects as seen from behind; showing auger-like conformation of wing.

Dorsal and ventral aspects, as seen from behind.

The ovary is small, rounded to elliptical, and one-celled, and contains a single slightly bent ovule sessile on the ventral suture (that is, springing from the back of the ovary); the micropyle points downwards.

Before fertilization the nucleus of the egg-cell divides and cuts off a ventral canal-cell; this cell may represent a second egg-cell.

In Central and South America alligators are represented by five species of the genus Caiman, which differs from Alligator by the absence of a bony septum between the nostrils, and the ventral armour is composed of overlapping bony scutes, each of which is formed of two parts united by a suture.

It is divided longitudinally by a partition separating a so-called" ventral "or prorachidial canal from a so-called" dorsal "or metarachidial canal.

The pectoral and ventral fins are so articulated as to perform the functions of feet, the fish being enabled to move, or rather to walk, on the bottom of the sea, where it generally hides itself in the sand or amongst sea-weed.

That part of the theca below the origins of the free arms is called the "dorsal cup"; the ventral part above the origins of the arms, serving as cover to the cup, is known as the "tegmen."

Thus the elements of the Pelmatozoan ventral groove are now detected in so different a structure as the echinoid ambulacrum, while an aboral nervous system, the diminished representative of that in crinoids, has been traced in all Eleutherozoa except Holothurians.

The epithelium of the outer surface was probably ciliated, and a portion of it in the preoral lobe differentiated as a sense-organ, with longer cilia and underlying nerve-centre, from which two nerves ran back below the ventral surface.

The radial water-vessels lie in grooves on the ventral side of flooring-plates (usually called "ambulacrals"); they and their podia are limited to the oral surface of the body and their extremities are separated from the FIG.

There are a few large dorsal, lateral and ventral armplates, and at the angles of the latter emerge FIG.

Although the present article does not discuss mammalian osteology in general (for which see Vertebrata), it is interesting to notice in this connexion that the primitive condition of the mammalian tympanum apparently consisted merely of a small and incomplete bony ring, with, at most, an imperfect ventral wall to the tympanic cavity, and that a close approximation to this original condition still persists in the monotremes, especially Ornithorhynchus.

The necks of the latter are short, the central series of cells consisting of ovum, ventral canal cell and one or two canal cells.

In Sphenophyllum fertile both the ventral lobes of the sporophyll (corresponding to the sporangiophores in other species) and the dorsal lobes, which in other species are sterile, were developed as peltate sporangiophores.

The older view was that it was a fertile segment of the leaf; and though its ventral position presents a difficulty, this must be regarded as a possible explanation; the occasional occurrence of sporangia on the lamina in Botrychium has been regarded as supporting it.

Azolla has roots depending from the lower surface of the stem into the water, while these organs are completely wanting in Salvinia, their place being taken functionally by highly divided leaves borne on the ventral surface of the stem.

The plants grow as a rule in marshy places, though some species of Marsilia are xerophytic. The creeping stem produces roots from the ventral surface and leaves from the dorsal surface; the leaves when young are circinately coiled.

The development of the sporocarp shows that it corresponds to a pinna, although when mature it may appear to occupy a ventral position in relation to the vegetative portion of the leaf.

This is facilitated by an important general change in the position of the parapodia; their basal attachments are all more ventral in position than in the Chaetopoda, and tend to approach from the two sides towards the mid-ventral line.

The parapodium is represented with its neural or ventral surface uppermost.

The postseptal coelom is partially divided by a ventral mesentery which is attached along the entire length of the convex.

The mouth (o) is in front of the tentacles, on the ventral side, and is overhung by a mobile praeoral hood, in which is the principal part of the nervous system.

The postseptal division is a coelomic space, partially subdivided by a ventral mesentery.

The ventral fin is also elongated, and all the fins are destitute of spines.

Two ventral bands composed of regular transverse rows of cilia are usually found.

An enlarged, frontal scale may cover the head, and a row of scales separates the ventral ciliated areas from one another, whilst two series of alternating rows cover the back and side.

The mouth is anterior and slightly ventral; it leads into a protrusible pharynx armed with recurved teeth that can be everted.

These papillae, which are found everywhere, are the primary papillae; they are covered with small, scale-like projections called secondary papillae, and are specially developed on the dorsal surface, less so on the ventral.

It is marked by a number of rings of papillae placed transversely to its long axis, the dorsal of which are pigmented like the dorsal surface of the body, and the ventral like the ventral surface.

At the narrow distal end of the leg there are on the ventral surface three or four (rarely five) spiniferous pads, each of which is continued dorsally into a row of papillae.

In some species certain of the legs bear on their ventral sides furrows with tumid lips and lined by smooth non-tuberculate epithelium; they are called coxal organs, and it appears that they can be everted.

The dissection is viewed from the ventral side, and the lips (L) have been cut through in the middle line behind and pulled outwards so as to expose the jaws (j), which have been turned outwards, and the tongue (T) bearing a median row of chitinous teeth, which branches behind into two.

Each of the ventral parts acquires an opening to the exterior, just outside the nerve-cord, G (After Sedgwick.) FIG.

B, Older gastrula stage, ventral view, showing elongated blastopore and primitive streak.

C, Ventral view of embryo with three pairs of mesoblastic somites, dumb-bell shaped blastopore and primitive s t r e a k.

D, Ventral view of embryo, in which the blastopore has completely closed in its middle portion.

The last section of this tube retains its connexion with the ventral portion of the somite, and so acquires an external opening, which is at first lateral, but soon shifts to the middle line, and fuses with its fellow, to form the single generative opening.

Dorsal surface arched and more darkly pigmented than the flat ventral surface.

Brain large, with two ventral hollow appendages; ventral cords widely divaricated, without distinct ganglia.

B, Endoderm has separated from the dorsal and ventral ectoderm.

The somite is represented as having divided on the left side into a dorsal and ventral portion.

The ventral portion (2) has assumed a tubular character, and has acquired an external opening.

A and feet with two primary papillae on the anterior side and one on the posterior side; outer jaw with one minor tooth at the base of the main tooth, inner jaw with no interval between the large tooth and the series of small ones; last fully developed leg of the male with enlarged crural gland opening on a large papilla placed on its ventral surface; coxal organs absent; the nephridial openings of the 4th and 5th pairs of legs are placed in the proximal spinous pad.

Last leg of the male with or without a large white papilla on its ventral surface for the opening of a gland, and marked papillae for the, crural glands are sometimes present on other legs of the male; well-developed coxal glands absent.

In marginal placentation the part of the carpel bearing the placenta is the inner or ventral suture, corresponding to the margin of the folded carpellary leaf, while the outer or dorsal suture corresponds to the midrib of the carpellary leaf.

The ovules (o) are attached to a central placenta, formed by the union of the five ventral sutures.

At other times they are vertical, as in Datura, where the ovary, in place of being two-celled, becomes four-celled; in Cruciferae, where the prolongation of the placentas forms a vertical partition; in Astragalus and Thespesia, where the dorsal suture is folded inwards; and in Oxytropis, where the ventral suture is folded inwards.

It is thus proved that the sporangiophore is not a mere sporangial stalk, but a distinct organ, in all probability representing a ventral lobe of the subtending bract.

The recently discovered species, Sphenophyllum fertile, while resembling Bowmanites Romeri in its peltate, bisporangiate sporangiophores, is peculiar in the fact that both dorsal and ventral lobes of the sporophyll were fertile, dividing in a palmate manner into several branches, each of which constitutes a sporangiophore.

The dorsal segments are sterile, corresponding to the bracts of Sphenophyllum Dawsoni, while the ventral segments constitute peltate sporangiophores, each bearing four sporangia, just as in a ax FIG.

There is good reason to believe that the ventral synangium of the Psiloteae corresponds to the ventral sporangiophore with its sporangia in the Sphenophyllales.

A parietal foramen; scales or bony scutes frequently present, especially on the ventral region, which is further protected by three large bony plates - interclavicle and clavicles, the latter in addition to cleithra.

In some the notochord remains for a long time exposed along the ventral surface, and, owing to the absence of cartilaginous formation around it, disappears without ever becoming invested otherwise than by a thin elastic membrane; it can be easily stripped off below the vertebrae in larval specimens on the point of metamorphosing.

In others, which represent the perichordal type, the greater share of the formation of the whole vertebra falls to the (paired) dorsal cartilage, but there is in addition a narrow ventral or hypochordal cartilage which fuses with the dorsal or becomes connected with it by calcified tissue; the notochord is thus completely surrounded by a thick sheath in tadpoles with imperfectly developed limbs.

The extinct Stegocephalia, on the other hand, were mostly protected, on the ventral surface at least, by an armour of overlapping round, oval, or rhomboidal scales, often very similar to those of Crossopterygian or ganoid fishes, and likewise disposed in transverse oblique lines converging forwards on the middle line of the belly.

The suckers are approximately the same in size, the ventral sucker being slightly anterior to the midline of the parasite.

There is degeneration of cardiac ventral epicardium and toxic cardiac necrosis, especially of the atrial lining with damage to spleen and heart.

These aircraft were converted on the production line, and retained the ventral gondola.

Our present focus of research is thus to examine the mechanisms and sources of ATP release from the ventral medulla much more closely.

Here we show that expression of active forms of MEK or of MAP kinase induces ventral mesoderm of the kind elicited by FGF.

There are 50 to 100 ventral pleats, from the chin to the umbilicus or slightly beyond the mid line.

The scientists found that a brain region called the ventral putamen lit up most strongly when people drank their favorite cola.

For example, lesions of canine superficial pyoderma (pustules) are most often seen on the ventral abdomen or medial thighs.

The ventral horns are where motor neurons leave the spinal cord.

Note the two suckers, the ventral sucker near the genital pore, and the oral sucker near the oesophageal gland.

The collarcavity (b.c. 2) is paired, although its ventral mesentery is not complete.

The ventral and lateral parts of the anterior margin of the collar constitute the so-called operculum (op.), a structure which not only acts as a lower lip, but must be important in separating the food-current produced by the cilia of the tentacles from the external apertures of the collar-canals and gill-slits.

The atlas is composed of three pieces; a pair of lateral ele ptz pt.z W " ments (the right and left dorsal arch pieces) joining above the spinal cord, and a ventral piece equivalent to the first basiventral elements, i.e.

Dorsal and ventral bending, even in the extended wing, is almost impossible.

Shell external, globular or ovoid; foot elongated, parapodia separate from ventral surface; genital duct diaulic. Lobiger.

Parapodia separate from ventral surface, and generally transformed into XI.

The abdomen consists of ten segments; at the end are either two or three long multi-articulate tails; in the male the ninth joint bears forcipated appendages; in the female the oviducts terminate at the junction of the seventh and eighth ventral segments.

Other forms show no indication of ever having been attached, while some that had been moored by means of a peduncle during the early portion of their existence have become detached at a more advanced stage of life, the opening becoming gradually cicatrized, as is so often seen in Leptaena rhomboidalis, Orthisina anomala, &c. Lastly, some species adhere to submarine objects by a larger or smaller portion of their ventral valve, as is the case with many forms of Crania, Thecidium, Davidsonia, &c. Some Cranias are always attached by the whole surface of their lower or ventral valve, which models itself and fills up all the projections or depressions existing on either the rock, shell or coral to which it adhered.

A, a segment of Bothriocephalus latus, showing the generative organs from the ventral surface; ex., excretory vessels; c., cirrus; c.p., cirrus pouch; v.d., vas deferens; v.o., vaginal opening; v., vagina; sh.g., shell-gland; od., oviduct; ov., ovary; y.g., yolk-gland; y.d., its duct; ut., uterus; u.o., uterine opening; the testes are not visible from this side; X 23 (from Sommer and Landois).

By reducing the tension to one quarter of its previous amount, the number of ventral segments will be seen to be increased to two, indicating that the first harmonic of the thread is now in unison with the solid, and consequently that its fundamental is an octave lower than it was with the former tension; thus confirming the law that n varies as S IT.

The liver first appears as an ento dermal hollow longitudinal outgrowth from the duo denum into the ventral mesentery.

The radula consists of a chitinous band bearing teeth, secreted by a ventral caecum of the pharnyx and moved by an apparatus of cartilage and muscles.

Rays simple or branched, capable of coiling, since the vertebrae articulate by surfaces of hour-glass shape; ventral arm-plates, and often the others, much reduced; spines reduced or absent.

Slugs are masters in secreting such slimy substances all over their body, especially on the ventral side.

Significant signal change in the region of the ventral striatum was also observed on such reversal errors, from a region of interest analysis.

This approach is suitable for all sizes of ventral hernia.

The concave dorsal fin begins above the base of the ventral fins.

It was, however, associated with a larger neural signal (over the contra-lateral ventral occipital cortex), than the unattended light.

Juveniles are grayish in color with the ventral fur being slightly paler.

In water, their center of mass was ventral to the muscles in the yolk mass.

A ventral vessel occurs on the anterior side of the metasome and forms a loop extending down the entire length of the stalk, while a " heart " projects into the cavity of the pericardium, probably connected on the ventral side of the notochord with the ventral vessel, and on its dorsal side with the dorsal vessel.

At their opposite ends the dorsal and ventral vessels are probably connected with one another by means of a splanchnic sinus surrounding the stomach.

Beneath the epidermis is a longitudinal layer of muscle-fibres which are separated into four distinct groups by the dorsal, ventral and lateral areas; these are occupied by a continuation of the epidermic layer; in the lateral areas run two thin-walled tubes with clear contents, which unite in the anterior part of the body and open by a pore situated on the ventral surface usually about a quarter or a third of the body length from the anterior end.

These processes stretch across the body cavity to be inserted in the dorsal and ventral middle lines.

In some species of Rana and Staurois inhabiting mountainous districts in south-eastern Asia, the larvae are adapted for life in torrents, being provided with a circular adhesive disk on the ventral surface behind the mouth, by means of which they are able to anchor themselves to stones.

In other species, however, a peculiar type of polystely is met with, in which the original diarch stele gives rise to se-called dorsal and ventral stelar cords which at first lie on the surface of the primary stele, but eventually at a higher level separate from it and form distinct secondary steles resembling the primary one.

If we consider a leaf of the common fern we find that in its young condition it is closely rolled up, the upper or ventral surface being quite concealed.

It is homologous with the distal ends of the ceratohyals or ventral elements of the hyoidean or second visceral arch.

Sometimes the pad is reduced to a ventral semi-ring or meniscus; it retains its largest almost original shape and size in the second vertebra, the axis or epistropheus, where it forms a separately ossifying piece which connects, and coossifies with, the odontoid process (the centrum of the atlas) and the centrum of the second vertebra.

Sometimes the ventral portions of these pads form paired or un paired little ossifications, then generally described as intercentra; such are not uncommon on the tail.

Dorsal vertebrae frequently have a ventral outgrowth of the centrum; these hypapophyses may be simple vertical blades, I-shaped, or paired knobs; they serve for the attachment of the thoracic origin of the longus collianticus muscle, reaching their greatest development in Sphenisci and Colymbidae.

The ventral portion of the neck is formed by the strong crista inferior, on the median side of which is the deep fosses subtrochanterica by which air sacs enter the humerus.

The ventral inner margin of the preacetabular portion of the ilium is attached to the pre-sacral vertebrae, whilst the inner and dorsal margin of the postacetabular portion is attached to the primary sacral and the postsacral vertebrae.

The flexor digitorum sublimis muscle arises fleshy from the long elastic band which extends from the inner humeral condyle along the ventral surface of the ulna to the ulnar carpal bone, over which the tendon runs to insert itself on the radial anterior side of the first phalanx of the second digit.

The last nerve which contributes to the ischiadic plexus leaves the spinal column in most birds either between the two primary sacral vertebrae, or just below the hindmost of them, and sends a branch to the pubic portion which is composed of post-ischiadic nerves, partly imbedded in the kidneys, and innervates the ventral muscles between the tail and pubis, together with those of the cloaca and copulatory organs.

The whole ventral surface of the pericardium is exposed when the sternum is removed.

Further, according to these muscles being inserted only upon the dorsal, or only upon the ventral, or on both ends of the semi-rings, we distinguish between an-, kat- and diacromyodi.

On the other hand, the diacromyodian type can have been developed only from a strong muscular basis which could split into a dorsal and a ventral mass; moreover, no Passeres are known to be intermediate between those that are diacromyodian and those that are not.

The next chamber, the urodaeum, is small, and receives in its dorso-lateral wall the ureters and the genital ducts; above and below this chamber is closed by circular folds, the lower of which, towards the ventral side, passes into the coating of the copulatory organ when such is present.

The penis, and its much reduced vestige of the female, is developed from the ventral wall of the proctodaeum.

It is protruded and retracted by special muscles which are partly attached to the ventral, distal end of the ilium.

The ventral region of the thoracic skeleton is complex, each segment usually possessing a median sternum with paired episterna (in front) and epimera (behind).

The glands occur in groups, and lead into common ducts which open usually so much reduced that the foremost apparent ventral sclerite of the abdomen represents the third sternite.

The well-known "fire-flies" of the tropics are large click-beetles (Elateridae), that emit light from paired spots on the prothorax and from the base of the ventral abdominal region.

In all Chaetopods this system consists of cerebral ganglia connected by a circumoesophageal commissure with a ventral ganglionated cord.