Limbs very slender; posterior nearly twice the length of the anterior.
3, Posterior end of alimentary canal.
This so-called third, upper or posterior conch is not a true conch, nor is that of the vestibulum; only the middle one forms a scroll, and this corresponds to the only one of reptiles and the lower of the mammals.
The median and posterior extension of the body of the sternum is a direct outgrowth of the latter, therefore FIG.
Thus the postcaval vein of the higher vertebrata is partly a new structure altogether, and is partly formed out of the pre-existing posterior cardinals.
One of these, broad and fleshy, is inserted upon the posterior surface of the distal third of the femur.
(4) A pair of thyrohyals, homologous with the posterior hyoid horns of mammals, i.e.
In relation to their parasitic habit one or two suckers are always developed, the one at the anterior and the other at the posterior end of the body.
They frequently progress after the fashion of a "looper" caterpillar, attaching themselves alternately by the anterior and the posterior sucker.
The posterior, so-called processus Zygomaticus is very variable; in many Galli it encloses a foramen by distally joining the orbital process.
Similarly during the growth of the bird the posterior end of the ilium connects itself with the transverse processes of vertebrae which were originally free, thus transforming them from caudals into secondary post-sacrals.
Of the metatarsals the fifth occurs as an embryonic vestige near the joint; the first is reduced to its distal portion, and is, with the hallux, shoved on to the inner and posterior side of the foot, at least in the majority of birds.
First two premolars with compressed and sharp-pointed crowns, and slightly developed anterior and posterior accessory basal cusps.
The squamosals form the posterior outer margin of the orbits and are frequently continued into two lateral downward processes across the temporal fossa.
Local government was modified by the law of the 10th of February 1889 and by posterior enactments.
5, 6 and 7, Anterior middle and posterior pairs of phagocytic organs.
One of these, the processus orbitatis posterior, often combines with an outgrowth of the alisphenoid, and may be, e.g.
Summits of the lower incisors, before they are worn, with a deep transverse groove, dividing it into an anterior and a posterior cusp. Canines long, strong and conical.
At the an ~ ~ tenor end are attached - two cilia or flagella In, , C the Vascular Cryptogams -- ~ the structure is much the;il ~.: -; same, but a more or less ~ ~ ~ spherical mass of cyto 4 i~- - ~ plasm remains attached .8 ~ :~ to the posterior spirals, -.
Then follows the rib-bearing portion and then the processus lateralis posterior; this also is the product of ribs, consequently the right and left processes together are equivalent to the xiphoid process or xiphisternum of the mammals.
2) where the anterior margin of the nasal is concave, and schizorhinal where this posterior border of the outer nares is continued backwards into a slit which extends beyond the frontal processes of the premaxilla.
pap,Posterior angular process of mandible.
The plates are compressed from before backwards, the anterior and posterior surfaces (as seen in the worn grinding face of the tooth) being nearly parallel.
Dorsolaterally the basisphenoid is joined by the alisphenoid, which forms most of the posterior wall of the orbit.
8) or saddle-shaped; the anterior surface is concave in a transverse, but convex in a vertical direction, which on posterior surface shows the conditions reversed.
In many birds the spaces between the metasternum and the posterior processes and again the spaces between this and the oblique process are filled up by proceeding ossification and either remain as notches, or as fenestrae, or they are completely abolished so that the breastbone is turned into one solid more or less oblong plate.
prior or posterior to the formation of the exclusive Judaean community, &c.).
One or two (anterior and posterior) suckers always present.
When the wing is folded the long glenoid surface of the head of the humerus is bordered above by the tuberculum externum or superius, in the middle and below by the tuberculum medium or inferius for the insertion of the coraco-brachialis posterior muscle.
The posterior patagium, the fold between trunk and inner surface of the upper arm, is stretched by the metapatagialis muscle, which is composed of slips from the serratus, superficialis, latissimus dorsi and the expansor secundariorum muscles.
The acetabulum is completely surrounded by these three bones, but its cup always retains an open foramen; from its posterior rim arises the strong antitrochanter.
Near the posterior pole of the fundus, but somewhat excentrically placed towards the temporal or outer side, is the fovea centralis, a slight depression in the retina, composed almost entirely of cones, the spot of most acute vision.
posterior mandibular process.
There are so many differences of detail that no line can be drawn between the one-celled funnel of Aeolosoma and the extraordinarily large and folded funnel of the posterior nephridia in the Oligochaete Thamnodrilus.
The molar teeth are six in number on each side, increasing in size from before backwards, and, as in the elephants, with a horizontal succession, the anterior teeth being lost before the full development of the posterior ones, which gradually move forward, taking the place of those that are destroyed by wear.
Clitellum commonly extensive and more posterior in position than in other groups.
and of the muscid flies, an anterior and a posterior endodermThe embryo thus becomes transferred to the dorsal face of the egg, rudiment both derived from the " endoblast " become apparent but at a later stage it undergoes reversion to its original ventral at an early stage, in close association with the stomodaeum and position.
Carriere's researches (1897) on the make its appearance simultaneously throughout the whole length of embryology of the mason bee (Chalicodoma) agree entirely with the the plate; the anterior parts are segmented before the posterior.
He finds that the endoderm arises may be readily distinguished, six of which subsequently enter into from an anterior and a posterior rudiment derived from the " endothe formation of the head, three going to the thorax and twelve to blast," that many of the cells of these rudiments wander into the the abdomen.
part by the yolk, and in part by those anterior and posterior rudiments Its composition has been the subject of prolonged difference of which usually form the mesenteron, but that in some Hexapoda opinion.
Comstock and C. Kochi believe that the labrum belongs to it,, The appendages of the posterior three or trophal segments become the parts of the mouth.
From these facts it appears that the anterior three divisions of the head differ strongly from the posterior three, which greatly resemble thoracic segments; hence it has been thought possible that the anterior divisions may represent a primitive head, to which three segments and their leg-like appendages were subsequently added to form the head as it now exists.
In the pelvic region, from about the level of the posterior end of the ischiadic plexus, the strand of each side becomes single again, passing ventrally over the transverse processes.
Another cartilage or ossification, the posterior sclerotic ring, occurs within the walls of the posterior portion of the cup, and surrounds, especially in the Pici and in the Passeres, the entrance of the optic nerve.
The olfactory perceptive membrane is restricted to the posterior innermost region of the nasal chamber, where it covers a slight bulging-out prominence on the nasal wall.
It seems that the posterior nephridia are mainly gonad ducts, and the gonads are developed in close association with the funnels.
The nasal cavity communicates with the mouth by the choanae or posterior flares, situated between the palatine process of the maxillary, the palatine and the vomer.
The venae hepaticae magnae join the vena cava posterior and thereby form with it the vena cava inferior.
There are five pairs of larger sacs belonging to the pulmonary system: - (1) prebronchial or cervical, extending sometimes far up the neck, even into the cranial cavities; the throat-bags of the prairie fowls (Cupidonia and Pedioecetes) are a further development; (2) subbronchial or interclavicular; (3 and 4) anterior and posterior thoracic or intermediate; (5) abdominal sacs.
historical criticism is faced with the established literary conclusions which, it should be noticed, place the Deuteronomic and priestly compilations posterior to the great changes at and after the fall of the northern monarchy, and, to some extent, contemporary with the equally serious changes in Judah.
In addition to these modifications, which are common to nearly all orchids, there are others generally but not so universally met with; among them is the displacement of the flower arising from the twisting of the inferior ovary, in consequence of which the flower is so completely turned round that the "lip," which originates in that part of the flower, conventionally called the posterior or superior part, or that S c ?
In most orchids the only stamen developed to maturity is the posterior one of the three opposite to the lip (anterior before the twisting of the ovary), the other two, as well as all three inner ones, being entirely absent, or present only in the form of rudiments.
The anterior nephridia, of which there are one to three pairs, contrast with the posterior series by their small funnels and large size, the posterior nephridia having a large funnel followed by a short tube.
In Lanice conchilega the posterior series of nephridia are connected by a thick longitudinal duct, which seems to be seen in its most reduced form in Owenia, where a duct on each side runs in the epidermis, being in parts a groove, and receives one short tubular nephridium only and occupies only one segment.
In Syllis there is also a "Heterosyllid" form in which the gonads are limited to a posterior region of the body which is further marked off from the anterior non-sexual segments by the oak-like setae.
In some Syllids this posterior region separates off from the rest, producing a new head; thus a process of fission occurs which has been termed schizogamy.
b 2, ditto, through posterior neuro pore.
forms and in terrestrial genera such as Cyclostoma; (2) the anterior pedal gland opening into the anterior groove of the foot, generally present in aquatic species; (3) dorsal posterior mucous glands in certain Cyclostomatidae.
Dermatocera, foot with a horn-shaped protuberance at its posterior end.
Lacuna, foot with two posterior appendages, marine, entirely aquatic. Cremnoconchus, entirely aerial, Indian.
Mantle with two posterior appendages; ctenidium large and capable of protrusion from pallial cavity.
Foot divided into two, posterior half bearing the operculum; a wide epipodial velum; shell turbinated.
Visceral sac and shell coiled in one plane; foot divided transversely into two parts, posterior part bearing an operculum, anterior part forming a fin provided with a sucker.
Foot broad, with two slender posterior appendages; operculum unguiculate.
Foot with anterior transverse groove; a posterior pallial tentacle; generally burrowing.
m, Mantle-flap reflected over the 0, Posterior cephalic tentacles.
Its superficial extent is seen when the folds covering the shell are cut away and the shell removed; the external surface forms a triangle with its base bordering the pericardium, and its apex directed posteriorly and reaching to the lefthand posterior corner of the shell-chamber.
On examination this is found to be the under surface of the posterior limb of the gland, the upper surface of which has just been described as lying beneath the shell.
When the pericardium is cut open from above in an animal otherwise entire, the anterior face of the kidney is seen forming the posterior wall of the pericardial chamber; on the deep edge of this face, a little to the left of the attachment of the auricle to the floor of the pericardium, is seen a depression; this depression contains the opening from the pericardium into the kidney.
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.
Posterior cephalic tentacle; and b, the eyes.
Hinder part of visceral hump. Posterior extremity of the foot.
a, b, Posterior and anterior cephalic tentacles.
Cephalic shield continuous with neck; twelve to fourteen stomachal plates; a posterior pallial filament passing through a notch in shell.
Posterior branchia triradiate.
Further on (pp. 101, 102) we find observations :as to the number of ribs which are attached to each of the " annexes " - there being sometimes more of them articulated to the anterior than to the posterior, and in certain forms no ribs belonging to one, all being applied to the other.
But the latter used this privilege wisely and well-not, after the manner of De Blainville and others subsequent to him, relying solely or even chiefly on the character afforded by the posterior portion of the sternum, but taking also into consideration those of the anterior, as well as of the in some cases still more important characters presented by the pre-sternal bones, such as the furcula, coracoids and scapulae.
3, E), which is to be derived from a Herpetomonadine type, the single, anterior flagellum of the ancestral parasite has been drawn backwards along one side of the body and now originates in the posterior half.
4, A - C); in Trypanomorpha it is in the posterior half of the body (fig.
most cases these granules are, if not confined to, chiefly distributed in the posterior (flagellate) half of the body (figs.
4, H) from carp, the anterior flagellum is much shorter than the free part of the posterior one, and evidently tending to disappear.
The anterior flagellum is longer than the free part of the posterior one.
Pulmonata with two pairs of tentacles, except Janellidae and Vertigo; these tentacles are invaginable, and the eyes are borne on the summits of the posterior pair.
A relation between objects of art described by Homer and the Mycenaean treasure was generally allowed, and a correct opinion prevailed that, while certainly posterior, the civilization of the Iliad was reminiscent of the Mycenaean.
Below each eye is a cheek area (gena), often divided into an anterior and a posterior part, while a distinct chin-sclerite (gula) is often developed behind the mouth.
The larva makes a globular case of .sand stuck together with fine silk spun, it is said, from a slender spinneret at the posterior end of the body.
The ganglia are crowded at the posterior end of the body as in leeches, and there is much tendency to the obliteration of the coelom as in that group. Pterodrilus and Cirrodrilus bear a few, or circles of, external processes which may be branchiae; Bdellodrilus and Astacobdella have none.
The gonads are, moreover, limited and fixed in numbers, and are practically invariably attached to the intersegmental septa, usually to the front septum of a segment, more rarely to the posterior septum.
14), and the presence of an anterior and posterior sucker, produce a looping mode of progression similar to that of a Geometrid larva.
The heart is usually posterior to the branchia (proso-branchiate).
ks.p, Posterior lobe of same.
This columella muscle is the same thing as the muscles adhering to the shell in Patella, and the posterior adductor of Lamellibranchs.
In the Gallinae the five well-known pieces or centres of ossification are said to consist of the two side-pieces of the second or middle series, and the three of the posterior.
At the same time he states that authors who have occupied themselves with the sternum alone have often produced uncertain results, especially when they have neglected its anterior for its posterior part; for in truth every bone of the skeleton ought to be studied in all its details.
In them the vomer, however variable, always tapers to a point anteriorly, while behind it includes the basisphenoidal rostrum between the palatals; but neither these nor the pterygoids are borne by its posterior divergent ends.
The Chanson de Roland, which cannot be posterior to the First Crusade - for the poem never alludes to it - already contains the idea of the Holy War against Islam.
In the posterior retractor the longitudinal fibres become united into one bundle, which, as noticed above, is inserted in the wall of the sheath.
The proboscis broken off and expelled is generally reproduced, the posterior ribbon-like end of this reproduced portion again fusing with the walls of the sheath.
There is reason to suppose that, when a wound is inflicted by the central stylet, it is envenomed by the fluid secreted in the posterior proboscidian region being at the same time expelled.
In the posterior portion this epithelium in certain Heteronemertea has a more glandular appearance, and sometimes the interior cavity is obliterated by cell-proliferation in this region.
The brain must be opening; u.l, superior brainlooked upon as the anterior thicklobe; pl., posterior brain-lobe.
No other intermediate stages have as yet been noticed between this arrangement and that of the Heteronemertini, in which a separate posterior brain-lobe receives a similar ciliated canal, and in which the oesophageal outgrowths have made their appearance and are coalesced with the nerve-tissue in the organ of the adult animal.
These posterior brain-lobes, which in all Heteronemertines are in direct continuity of tissue with the upper pair of principal lobes, cease to have this intimate connexion in the Metanemertini; and, although still constituted of (I) a ciliated duct, opening out externally, (2) nervous tissue surrounding it, and (3) histological elements distinctly different from the nervous, and most probably directly derived from the oesophageal outgrowths, they are nevertheless here no longer constantly situated behind the upper brain-lobes and directly connected with them, but are found sometimes behind, sometimes beside and sometimes before the brain-lobes.
The posterior portion of the intestine is specially characterized by the appearance of the intestinal diverticula horizontally and symmetrically placed right and left and opposite to each other.
They are in direct connexion with each other both at the posterior and at the anterior end of the body.
At the posterior end they communicate together by a T-shaped connexion in a simple and uniform way.
18, in the Heteronemertines the lateral stems, while entirely uniform all through the posterior portion of the body, no longer individually exist in the oesophageal region, but here dissolve themselves into a network of vascular spaces surrounding this portion of the digestive tract.
Anteriorly it finally communicates with the lacunae just mentioned, which surround the oesophagus, bathe the posterior lobes of the brain, pass through the nerve ring together with the proboscidian sheath, and are generally continued in front of the brain as a lacunar space in the muscular tissue, one on each side.
No trace of nephridia is found posterior to the oesophagus.
liber, edited by Staudlin (1820-1829); and from the Liber posterior, edited by A.
The nervous system is represented by an oesophageal collar and a suboesophageal ganglion, whence paired nerves pass outwards to innervate the anterior extremity and backwards towards its posterior end.
The two testicles, which extend far back into the posterior part of the body, are long and tubular.
The commoner European slugs of small size all belong to the genus Limax, in which the opening of the mantle-chamber is posterior.
There is a "stay" called the "ligament" which runs from the hinder end of the proboscissheath to the posterior end of the body.
m The "bell" swallows the matured embryos and passes them on into the uterus, and thus out of the body via the oviduct, which opens at one end into the uterus and at the other on to the exterior at the posterior end of o.-- the body.
continuous series, with massive, quadrate, transversely ridged or complex crowns--the posterior premolars usually resembling the molars in structure.
The other upper premolars and molars all formed on the same plan and of nearly the same size, with four roots and quadrate crowns, rather wider transversely than from before backwards, each having four columns, connected by a pair of transverse ridges, anterior and posterior.
The first lower premolar compressed in front; the others composed of a single pair of transverse crests, with a small anterior and posterior basal ridge.
The posterior valley is formed behind the posterior transverse ridge, and is bounded externally by a backward continuation of the outer wall and behind by the cingulum.
The middle valley is often intersected by vertical "crista" and "crochet" plates projecting into it from the anterior surface of the posterior transverse ridge or from the wall, the development of which is a useful guide in discriminating species, especially those known only by teeth and bones.
9, Posterior valley.
2, Posterior surface.
The dorsal skeletal elements of the thorax and of the anterior six abdominal segments unite with the wing-cases to form a large respiratory chamber, containing five pairs of tracheal gills, with lateral slits for the inflow and a posterior orifice for the outflow of water.
The wings are carried erect: the anterior pair large, with numerous longitudinal nervures, and usually abundant transverse reticulation; the posterior pair very much smaller, often lanceolate, and frequently wanting absolutely.
Of these divisions of the coelom the first two communicate with the exterior by means of a pair of ciliated pore-canals placed at the posterior end of their respective segments.
The proboscis-gut occurs as an outgrowth from the anterior dorsal wall of the collar-gut, and extends forward into the basal (posterior) region of the proboscis, through the neck into the proboscis-coelom, ending blindly in front.
The nervous system is thus essentially epidermal in position and diffuse in distribution; but an interesting concentration of nerve-cells and fibres has taken place in the collar-region, where a medullary tube, closed in from the outside, opens in front and behind by anterior and posterior neuropores.
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.
the gill-slits may be stated briefly as follows: - (a) the presence of two kinds of branchial bars in all species and also of small cross bars (synapticula) in many species; (s) numerous gill slits, from forty to more 1 - _ than a hundred pairs; (y) the addition of new gill-slits by fresh perforation at the posterior end of the pharynx throughout life.
Without attempting to answer this question categorically, it may be pointed out that within the limits of the family (Ptychoderidae) which is especially characterized by their presence there are some species in Y art dY YY cts, posterior limit of collar.
In the Trimerellidae, for example, some of the muscles are attached to a massive or vaulted platform situated in the medio-longitudinal region of the posterior half or umbonal portion of both valves.
The body of the Brachiopod v usually occupies about the posterior half of the space within the shell.
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.
In Rhynchonella, where there are two pairs of kidneys, the internal opening of the anterior pair is supported by the gastroparietal band and that of the posterior pair by the ileoparietal band.
It is a remarkable fact that in Discinisca, although the vessels to the lophophore are arranged as in other Brachiopods, no trace of a heart or of the posterior vessels has as yet been discovered.
Posterior occlusor muscle.
Mark's narratives of the sepulture by Joseph of Arirathea and of the empty tomb are taken as posterior to St Paul; the narratives of the infancy in Matthew and Luke as later still.
They are distinguished by having one of the five blue or yellow coloured sepals (the posterior one) in the form of a helmet; hence the English name monkshood.
PLR, Posterior lateral rod or RAP, Right anterior process.
PLP, Posterior lateral process.
1 with the addition of NF, neural fossa protecting the aggregated ganglia of the central nervous system; PVP, left posterior ventral process; PMP, posterior median process.
The tergites of this region and those of the following region, the metasoma, are fused to form a second or posterior carapace in Limulus, whilst remaining free in Scorpio.
pp, Posterior process (same as PLP in fig.
pf, Posterior flap or diaphragm of Newport.
- Ventral view of the posterior carapace or meso-metasomatic (opisthosomatic) fusion of Limulus polyphemus.
The y are really excretory glands, and communicate with the exterior by a very minute aperture on the posterior face of the coxa of the fifth limb on each side.
The scorpion's entosternite gives rise to outgrowths, besides the great posterior flaps, pf, which form the diaphragm, unrepresented in Limulus.
is similar to that in Limulus, whilst the imbricate triangular pieces of the posterior median region resemble the similarlyplaced structures of Limulus in a striking manner.
(After Lankester.) placed in the same somites as those of Scorpio, but there is one additional posterior pair.
v., 1892.) heart differs in Limulus from the arrangement obtaining in Scorpio, in that a pair of lateral commissural arteries exist in Limulus (as described by Alphonse Milne-Edwards (6)) leading to a suppression of the more primitive direct connexion of the four pairs of posterior II.
a 2 to a 5, Posterior borders of the chitinous bases of the coxae of the second, third, fourth and fifth prosomatic limbs.
But most important of the evidences presented by the trilobites of affinity with Limulus, and therefore with the Arachnida, is the tendency less marked in some, strongly carried out in others, to form a pygidial or telsonic shield - a fusion of the posterior somites of the body, which is precisely identical in character with the metasomatic carapace of Limulus.
40) the anterior and posterior carapaces constitute almost the entire body, the two carapaces being connected by a mid-region of only two free somites.
It has been held that the forms with a small number of somites marked in the posterior carapace and numerous free somites between the anterior and posterior carapace, must be considered as anterior to those in which a great number of posterior somites are traceable in the metasomatic carapace, and that those in which the traces of distinct somites in the posterior or metasomatic carapace are most completely absent must be regarded as derived from those in which somites are well marked in the posterior 1 The writer is indebted to R.
On the other hand, it may well be doubted whether the pygidial or posterior carapace is primarily due to a fusion of the tergites of somites which were previously movable and well developed.
a, Restored thoracic limbs in transverse section of the animal; b, section across a posterior somite; c, section across one of the sub-terminal somites.
(From Korschelt and Heider.) quently take place (as in all Arthropoda) at the posterior extremity of the body, whilst excalation of somites may occur at the constricted areas which often separate adjacent " regions," though there are very few instances in which it has been recognized.
The dotted line on somite I indicates the position of the genital operculum which was probably provided with branchial lamellae.] well-developed somites is present and the posterior ones form a long tail-like region of the body.
There is also a pair of narrow tergal sclerites interposed between the anterior and posterior shields.
b, Posterior plate of the prosomatic carapace.
s1 2, Posterior sternal plate of the prosoma.
(Original by Pickard-Cambridge and Pocock.) elements generally distinguishable at the anterior and posterior ends respectively of the large mesosternum.
63,stg), as in the Amblypygi, or with the posterior pair, rarely the anterior pair as well, replaced by tracheal tubes.
Between the bases of the prosomatic limbs an anterior III and a posterior sternal plate (black) are seen.
In front of it the narrow waist is formed by the soft sternal area of the praegenital somite; 2, the sternite of the 2 second opisthosomatic somite covering the posterior pair of lung-sacs; and 4, the spinning appendages (limbs) of the opisthosoma; a, inner, b, outer ramus of the appendage; I I, sternite of the eleventh --
The posterior pulmonary sacs (except in Hypochilus) replaced by tracheal tubes; the anterior and posterior pairs replaced by tracheal tubes in the Caponiidae.
Remaining pairs of appendages with their basal segments immovably fixed to the sternal surface, similar in form, the posterior three pairs furnished with two claws supported on long stalks; the basal segments of the 6th pair bearing five pairs of tactile sensory organs or malleoli.
- Dorsal plate of prosoma (carapace) narrowed in front; the appendages of the 1st pair small, much narrower, taken together, than the posterior border of the carapace.
- Dorsal plate of prosoma scarcely narrowed in front; the appendages of the 1st pair large, not much narrower, taken together, than the posterior border of the carapace.
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.
We have no manuscript of any prose Arthurian romance earlier than the 13th century, to which period Gaston] Paris assigned them; they are certainly posterior to the verse romances.
The lower jaw projects more or less beyond the upper, the mental barble is small, sometimes rudimentary, the vent is below the posterior half of the first dorsal fin, and there is a dark spot in the axil of the pectoral fin.
In such cases the paths of degeneration are so neatly defined that, when the tissues are prepared after death by modern methods, they are plainly to be seen running along certain columns, the subdivisions of which in the normal state may hardly be distinguishable one from another: some run in strips along the periphery of the spinal cord, at its anterior, middle or posterior segments, as the case may be; in other cases such strips occur within its substance, whether along columns of cells or of white matter.
The latter again are divided into Metanopsilae (in which the metanotum or posterior region of the thorax is bare) and Metanotrichae (in which the metanoturn is clothed with bristles or scales).
The anterior and posterior ends of the body are well defined.
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.
The excretory pore is terminal and posterior in endoparasitic forms: paired, anterior and dorsal in the ectoparasitic class.
intestine; sc; posterior suckers; yk, yolk-glands.
- Ectoparasitic Trematodes, in which a large posterior adhesive apparatus is present and is usually accompanied by a pair of suckers placed anteriorly in relation to the mouth.
The large posterior organ of attachment is usually wheel-shaped and provided with hooks; but the ridges may become separated 'FIG.
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.
The excretory system is highly developed and opens at the posterior extremity by a paired muscular bladder.
It is posterior (Amphistomidae), or anterior (Gasterostomidae).
Specimens in which the posterior horn has attained a length as great as or greater than the anterior have been separated under the name of R.
They may be characterized as very elongated reptiles without limbs (unless with tiny vestiges of posterior limbs), without eyelids and external ear openings, with the teeth anchylosed to the supporting bones, a bifid slender tongue which is telescoped into its basal half, and with a transverse vent.
of scaly reptiles with movable quadrate bones; with a transverse vent, near the posterior lateral corners of which open the eversible, paired copulatory organs.
In some all the teeth are nearly of the same size; others possess in front of the jaws (Lycodonts) or behind in the maxillaries (Diacrasterians) a tooth more or less con spicuously larger than the rest; whilst others again are distinguished by this larger posterior tooth being grooved along its outer face.
f, Posterior frontal.
One or more of the posterior maxillary teeth are grooved.
- The postfrontal bones are restricted to the posterior border of the orbits.
Characterized by possessing only a few teeth, on the posterior part of the maxillaries, on the palatines and Coronelline Nymphophidium, the same effect is reached by two prominences at the base of the skull.
- One, or a few, of the posterior maxillary teeth have a groove or furrow in front, which conducts the secretion of the enlarged upper labial glands.
a shield intercalated between the two preoculars and the posterior nasal; below the loreal lies the pit.
In the latter case the larva crawls about the bottom of the water or up the stems of plants, with its thickly-chitinized head and legs protruding from the larger orifice, while it maintains a secure hold of the silk lining of the tube by means of a pair of strong hooks at the posterior end of its soft defenceless abdomen.
round the proboscis and in the two posterior caudal spines.
Dr Leith-Adams, working from more abundant materials, has shown that the number of ridges of each tooth, especially those at the posterior end of the series, is subject to individual variation, ranging in each tooth of the series within the following limits: 3 to 4, 6 to 9, 9 to 12, 9 to 15, 14 to 16, 18 to 27 - excluding the small plates, called " talons," at each end.
The anterior pair reach far beyond the end of the abdomen; the posterior are narrower and not so long.
No 1 Internally there Is a great difference in the form of the posterior margin of the sternum, as long ago remarked by Nitzsch.
The sexes are not distinct, the sexual organs being represented by a pair of testes and a single ovary, which open together into the posterior end of the alimentary canal.
According to the ordinary laws of research, the book, being written at a time long posterior to the events it records, can have only a secondary value, although that is no reason why here and there valuable material should not have been preserved.
16 54" (1655); "Tractatus duo, prior de cycloide, posterior de cissoide et de curvarum turn linearum dthivvec turn superficierum RrXarva,uw" (1659); "Mechanica, sive de motu tractatus geometricus" (three parts, 1669-1670-1671); "De algebra tractatus historicus et practicus, ejusdem originem et progressus varios ostendens" (English, 1685); "De combinationibus alternationibus et partibus aliquotis tractatus" (English, 1685) "De sectionibus angularibus tractatus" (English, 1685); "De angulo contactus et semicirculi tractatus" (1656); "Ejusdem tractatus defensio" (1685); "De postulato quinto, et quinta definitione, lib.
The posterior end of the organ is positive, the anterior negative, and the current, passes from the tail to the head.
This version is quoted as Syr H (and when necessary Syr Hc* or Syr H mg) and by Tischendorf as SyrP (= Syra posterior).
The pallial line, which is the line of attachment of the mantle parallel to the edge of the shell, is not indented by a sinus at the posterior end.
In the entire animal the posterior end projects slightly more than the anterior from the region of the umbones.
The foot has a byssus gland on its posterior surface.
The tongue is generally beset with more or less scaly or velvety papillae and has always a well-marked posterior margin, while the anterior portion may or may not be more or less retractile into the posterior part.
This appendage is merely a fold of the skin, ornamental and sexual; it has no cavity in its interior, and has no communication with the mouth or with the respiratory organs; it is supported by the posterior horns of the hyoid bone, and can be erected and spread at the will of the animal.
- Pleurodont; teeth solid, sometimes (Ophiosaurus) grooved; anterior part of tongue emarginate and retractile into the posterior portion; osteoderms on the body, and especially on the head where they are roofing over the temporal fossa; entirely zoophagous and ovo-viviparous.
4) was found nearly complete in the beds of the Morrison formation, Upper Jurassic of central Wyoming, U.S.A. Near it was discovered the posterior portion of the skeleton of a giant herbivorous dinosaur (Brontosaurus Marsh).
It presents a single pair of muscles attached along its inner wall which run up and form a muscular girdle round the body in its posterior third.
Pedalion presents a pair of ciliated toes in the posterior region of the body (fig.
The posterolateral angles of the gena are commonly produced into spiniform processes, which may project backwards beyond the middle of the body as in Paradoxides, or considerably beyond its posterior termination as in Trinucleus or Ampyx.
In the majority of Trilobites this groove passes backwards from the anterior or anterolateral edge of this plate to its posterior or postero-lateral border, dividing it into an inner portion continuous with the flabellum and fused tergal regions, and an outer portion bearing the eye.
Those genera, like Paradoxides, Olenus, Asaphus, Phillipsia and others, in which this groove cuts the posterior edge of the head-shield on the inner side of its angle are referred to the Opisthoparia; those, like Dalmanites and Phacops, in which it cuts the lateral border in front of the posterior angle, belong to the Proparia.
But in certain genera, like Conocoryphe, Calymmene and Triarthrus, it cuts the margin of the head-shield so close to the posterior angle that the distinction between the two groups practically breaks down.
In all other Trypanosomes there is only one flagellum, which is invariably attached to the body in the same manner as the posterior one of biflagellate forms. This flagellum, however, is most probably not to be considered homologous in all cases.
The point of insertion of the attached (posterior) flagellum into the body, and, consequently, the commencement of the undulating membrane may be almost anywhere in the anterior half of the body, but is usually near the extremity.
2 It possesses only a single pair of posterior " emarginations on its sternum, in this respect resembling the Ruff.
The crown of the third molar is nearly as long as those of the first and second together, having, in addition to the four principal lobes, a large posterior heel, composed of clustered conical cusps, and supported by additional roots.
The milk-dentition, and even the early condition of the permanent dentition, is formed on the same general type as that of Sus, except that certain teeth are absent, the formula being 13 i cl, total 34; but as age advances all the teeth have a tendency to disappear, except the canines and the posterior molars, but these, which in some cases are the only teeth left in the jaws, attain an extraordinary development.
The lower canines are much more slender, but follow the same curve; except on the posterior surface, their crowns are covered with enamel; both pairs of canines are large in the two sexes.
When hardened in situ its shape is that of a right-angled, triangular prism showing five surfaces - superior, anterior, inferior, posterior and right lateral which represents the base of the prism.
At its posterior margin the peritoneum of the great sac is reflected on to the diaphragm to form the anterior layer of the coronary ligament.
The posterior surface is more complicated (see fig.
Again starting from the right side, two impressions are seen; the anterior one is for the hepatic flexure of the colon, and the posterior for the upper part of the right kidney.
The posterior boundary of the quadrate lobe is the transverse fissure, which is little more than an inch long and more than half an inch wide.
- The Liver from below and behind, showing the whole of the visceral surface and the posterior area of the parietal surface.
The posterior or attached border is uppermost.
The chief points in which they vary are - (1) in the structure of the ctenidia or branchial plates; (2) in the presence of one or of two chief muscles, the fibres of which run across the animal's body from one valve of the shell to the other (adductors); (3) in the greater or less elaboration of the posterior portion of the mantle-skirt so as to form a pair of tubes, by one of which water is introduced into the sub-pallial chamber, whilst by the other it is expelled; (4) in the perfect or deficient symmetry of the two valves of the shell and the connected soft parts, as compared with one another; (5) in the development of the foot as a disk-like crawling organ (Arca, Nucula, Pectunculus, Trigonia, Lepton, Galeomma), as a simple plough-like or tongueshaped organ (Unionidae, &c.), as a re-curved saltatory organ (Cardium, &c.), as a long burrowing cylinder (Solenidae, &c.), or its partial (Mytilacea) or even complete abortion (Ostraeacea).
1, Posterior (pedal) adductor muscle of the shells.
m, Posterior retractor muscle of the foot.
o, Posterior labial tentacle.
i [i]) is called the umbonal area; the great anterior muscular surface h is that of the anterior adductor muscle, the posterior similar surface i is that of the posterior adductor muscle; the long line of attachment u is the simple " pallial muscle," - a thickened ridge which is seen to run parallel to the margin of the mantle-skirt in this Lamellibranch.
It is the approximate equality in the size of the anterior and posterior adductor muscles which led to the name Isomya for the group to which Anodonta belongs.
In fact all Lamellibranchs begin with a condition in which there is only one adductor, and that not the posterior but the anterior.
Then the posterior adductor develops, and becomes equal to the anterior, and finally in some cases the anterior becomes smaller or disappears.
Their appearance and position suggest that they are in some way related morphologically to the gill-plates, the anterior labial tentacle being a continuation of the outer gill-plate, and the posterior a continuation of the inner gill-plate.
h, Posterior adductor.
k, Posterior labial tentacle.
p.a, Posterior adductor muscle.
Posterior end of the gill (ctenidium).
B,Diagram of the posterior face of a single complete filament with descending ramus and ascending ramus ending in a hook-like process;ep.,ep.,the ciliated junctions; il,j ., inter-lamellar junction.
Posterior adductor muscle.
r, Line of origin of the posterior labial tentacle.
Hind region of foot in Ano- Region altogether posterior to the foot in Anodonta.
18, A), and giving off an anterior and a posterior artery, FIG.
indicate the course of fluid ab, Posterior, cut remnants of the from the pericardium outintestine and ventricle.
Posteriorly beneath the posterior adductors, and covered only by a thin layer of elongated epidermal cells, are the visceral ganglia.
Formerly the posterior pair of ganglia were identified as simply the osphradial ganglia, and the anterior pair as the cerebral, pleural and visceral ganglia united into a single pair.
Anodonta has no eyes of any sort, and the tentacles on the mantle edge are limited to its posterior border.
21), so that its fibres join the anterior faces of the nerve-end cells as in Vertebrates, instead of their posterior faces as in the cephalic eyes of Mollusca and Arthropoda; moreover, the lens is not a cuticular product but a cellular structure, which, again, is a feature of agreement with the Vertebrate FIG.
After the formation of the gastrula by epibole the larva becomes enclosed by an ectodermic test covering the whole of the original surface of the body, including the shell-gland, and leaving only a small opening at the posterior end in which the stomodaeum and proctodaeum are formed.
The test is really a ciliated velum developed in the normal position at the apical pole but reflected backwards in such a way as to cover the original ectoderm except at the posterior end.
In Yoldia and Nucula proxima the ova are set free in the water and the test-larvae are free-swimming, but in Nucula delphinodonta the female forms a thin-walled egg-case of mucus attached to the posterior end of the shell and in communication with the pallial chamber; in this case the eggs develop and the test-larva is enclosed.
- One row of branchial filaments is directed dorsally, the other ventrally; the mantle has a long posteroventral suture and a single posterior aperture; the labial palps of each side are fused together; shell elongate; hinge without teeth; periostracum thick.
- Labial palps free, very broad, and provided with a posterior appendage; branchial filaments transverse; shell has an angular dorsal border; mantle open along its whole border.
- Like the Nuculidae, but mantle has two posterior sutures and two united siphons.
Very asymmetrical, with a single large posterior adductor.
Symmetrical; mantle open throughout its extent; generally with well developed anterior and posterior adductors.
Parallelodontidae.-Shell as in Arca, but the posterior hinge teeth elongated and parallel to the cardinal border.
Lyrodesmidae.-Extinct; shell inequilateral, posterior side shorter; hinge short, teeth in form of a fan.
Mantle has a posterior suture.
Megalodontidae.-Shell 1a, tr, Upper and lower inequilateral, thick; posterior siphons adductor impression on a myo ms, Siphonal muscle of the phorous apophysis.
mp, Posterior Dicerocardium; Jurassic. muscle.
A bulb on the posterior aorta.
Cardiliidae.-Shell very high and short; dimyarian; posterior adductor impression on a prominent apophysis.
- Shell thin, gaping widely at the posterior end; anterior adductor much reduced; mantle extensively closed; siphons long, united.
- Shell globular, covering only a small portion of the vermiform body; heart on ventral side of rectum; a single aorta; siphons long, united and furnished with two posterior calcareous " pallets."
- Mantle with fourth aperture; siphons very long, completely united, naked, incompletely retractile; foot small, with posterior appendage.
An Aristotelian work often goes on continuously at first, and then becomes disappointing by suddenly introducing discussions which break the connexion or are even inconsistent with the beginning; as in the Posterior Analytics, which, after developing a theory of demonstration from necessary principles, suddenly makes the admission, which is also the main theory of science in the Metaphysics, that demonstration is about either the necessary or the contingent, from principles either necessary or contingent, only not accidental.
3) the Posterior Analytics, i.
Hence the Posterior Analytics, which is Aristotle's authoritative logic of science, is of peculiar interest because, after beginning by defining science as investigating necessary objects from necessary principles (i.
He got so far as gradually to write short discourses and long treatises, which we, not he, now arrange in the order of the Categories or names; the De Interpretatione on propositions; the Analytics, Prior on syllogism, Posterior on scientific syllogism; the Topics on dialectical syllogism; the Sophistici Elenchi on eristical or sophistical syllogism; and, except that he had hardly a logic of induction, he covered the ground.
But he never called any of these a division of all logic. Thirdly, he had no one name for logic. In the Posterior Analytics (i.
Poste wrote translations of the Posterior Analytics and Sophistici Elenchi; R.
The upper half or body of the uterus is somewhat triangular with its base upward, and has an anterior surface which is moderately flat, and a posterior convex.
6, B), the anterior and posterior walls of which are in contact.
The canal of the cervix is about an inch long, and is spindle-shaped when looked at from in front; its anterior and posterior walls are in contact, and its lining mucous membrane is raised into a pattern which, from its likeness to a cypress twig, is called the arbor vitae.
The vagina is a dilatable muscular passage, lined with mucous membrane, which leads from the uterus to the external generative organs; its direction is, from the uterus, downward and forward, and its anterior and posterior walls are in contact, so that in a horizontal section it appears as a transverse slit.
Owing to the fact that the neck of the uterus enters the vagina from in front, the anterior wall of that tube is only about 21 in., while the posterior is 31.
Posterior superior iliac spine Ureter Great sciatic notch Vas deferens; Spine of ischium Vas deferens Seminal vesicle Bladder wall Levator ani Prostate 9, ?
It is often described as formed of three lobes two lateral and a median or posterior, but careful sections and recent research throw doubt on the existence of the last.
When it is slit open from in front a longitudinal ridge is seen in its posterior wall, which is called the verumontanum or crista urethra, and on each side of this is a longitudinal depression, the prostatic sinus, into which numerous ducts of the prostate open, though some of them open on to the antero-lateral surface.
Posterior superior iliac spine Cut end of rectum Apex of sacrum Great sciatic notch Ureter Peritoneum Spine of ischium Bladder wall Seminal vesicle Tuberosity of ischium Ischio-rectal fossa Cut end of rectum External sphincter ani Gluteus maximus better seen in young the prostate the urethra runs more forward for about threequarters of an inch, lying between the two layers of the triangular From C. S.
In the primitive condition there is one on each side in the mantle cavity, towards the posterior end of the body.
Thus in the primitive mollusc the mantle-cavity contains a symmetrical group of structures at the posterior end of the body, and this group of structures is called the pallial complex.
The heart is situated in the pericardium on the dorsal side of the intestine and at the posterior end of the animal.
In more specialized forms a posterior aorta passes backwards from the ventricle, as in Gastropods and the majority of Lamellibranchs.
h.a, Posterior adductor.
The mouth is divided into two cavities communicating by a narrow orifice, the anterior one containing the incisors and the posterior the molars, the hairy skin of the face being continued inwards behind the incisors.
Riggs, is the unusual development of the premolar to the exclusion of the posterior teeth.
In Pelargonium the flower is zygomorphic with a spurred posterior sepal and the petals differing in size or shape.
The upper incisors have persistent pulps, and are curved longitudinally, forming a semicircle as in rodents; they are, however, not flattened from before backwards as in that order, but prismatic, with an antero-external, an anterointernal and a posterior surface, the first two only being covered with enamel; their tips are consequently not chisel-shaped, but sharp-pointed.
In this case also the posterior end of the larva represents the anterior end of the ant.
The wings are transparent and are black-bordered and black-barred, the anterior wing having two black bars and the posterior one.
Narrowing of the posterior portions of the spider's cephalothorax and sometimes of the anterior end of the abdomen reproduces the slender waist of the ant, and frequently transverse bands of hairs represent the segmentation of this region in the insect.
The mimicry of these insects therefore is synaposematic; but some, at all events, of the flies like the Bombylid Exoprosopa umbrosa, probably form pseudaposematic elements in the group. Into another category Hymenoptera enter not as models but as mimics, the models being inedible Malacodermatous beetles mostly belonging to the genus Lycus and characterized by orange coloration set off by a large black patch upon the posterior end of the elytra and a smaller black spot upon the thorax.
The anterior margin of each valve except the first is provided with two projections called sutural laminae which underlie the posterior margin of the preceding valve.
The series of gills may extend the whole length of the body in the pallial groove, or may be confined to the posterior end.
Each gill has the structure of a typical molluscan ctenidium, consisting of an axis bearing an anterior and posterior row of filaments or lamellae.
Both the openings are close together, the external opening being just in front of the principal gill near the posterior end of the body.
A simple gonaduct on each side arises from the gonad near its posterior end and passes first forwards, then backwards, and lastly outwards to the external opening in the pallial groove, anterior to the renal aperture.
b, Posterior extremity.
There is also in some genera a median retractile sensory papilla on the dorsal posterior surface above the rectum, not covered by the cuticle.
The body chamber (reduced pallial chamber, conis worm-like and cylindritaining the concealed_pair of ctenidia) cal, the posterior half a to the right.
little thicker than the an terior; the posterior ex tremity forms the enlarged funnel-like branchial or cloacal chamber.
The chief difference is that the gonad or generative portion of the coelom is single and median, opening into the pericardium by a single posterior aperture.
In the Siebengebirge the little crater of Roderberg, with its lavas and scoriae of leucite-basalt, is posterior to some of the Pleistocene river deposits.
Histriodrilus resembles Saccocirrus in the possession of two posterior adhesive processes, and to some extent in the structure of the complex genital organs, which, however, are restricted to a single segment.
Characters: Barbels, three to six pairs; pharyngeal teeth in one row, in moderate number; anterior part of the air-bladder divided into a right and left chamber, separated by a constriction, and enclosed in a bony capsule, the posterior part free or absent.
GUENON (from the French, = one who grimaces, hence an ape), the name applied by naturalists to the monkeys of the African genus Cercopithecus, the Ethiopian representative of the Asiatic macaques, from which they differ by the absence of a posterior heel to the last molar in the lower jaw.
The limbs of the U are further twisted together in a looser or tighter coil, the axis of which may be traversed by a "spindle" muscle arising from the posterior end of the body.
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.
(vi.) Aspidosiphon, with 19 species, is easily distinguished by a calcareous deposit and thickened shield at the posterior end and at the base of the introvert, which is eccentric. (vii.) Cloeosiphon has a calcareous ring, made up of lozenge-shaped plates, round the base of its centric introvert.
The posterior nares or choanae open far behind in the roof of the mouth, in recent forms within the pterygoids.
Dorsally the posterior nares open into this cavity.
It is of course written in Greek, and consists of parts of the substance of the Codex and the Digest, thrown together and often altered in expression, together with some matter from the Novels and imperial ordinances posterior to Justinian.
In the first it is a biconvex lens, from which segments are continually cut off parallel to the posterior surface; and in the second an elongated dome, from which segments are cut off by a transverse wall.
The thallus is somewhat spherical and unicellular, exhibiting a distinction between anterior and posterior extremities, and dorsal and ventral surfaces.
The most noteworthy point of distinction is in the skull, in which the facial portion is sharply bent down on the posterior basal axis in the fashion characteristic of the hollow-horned ruminants (oxen, antelopes, &c.), and the American prongbuck, instead of running more or less nearly parallel to the same, as in deer.
Above the brow-tine is developed a second palmated tine, which appears to represent the bez-tine of the red-deer; there is no trez-tine, but some distance above the bez the beam is suddenly bent forward to form an "elbow," on the posterior side of which is usually a short back-tine; above the back-tine the beam is continued for some distance to terminate in a large expansion or palmation.
The male is distinguishable from the female by the presence of a fork at the posterior end of the body.
The preacetabular portion of the ilium is shorter than the posterior half.
The hind-limb is typically avine, with intertarsal joint, distally reduced fibula, and the three elongated metatarsals which show already considerable anchylosis; reduction of the toes to four, with 2, 3, 4 and 5 phalanges; the hallux is separate, and as usual in recent birds posterior in position.
On literary-historical grounds the Pentateuch in its present form is post-exilic, posterior to the old monarchies and to the ideals of the earlier prophetical writings.
Genesis - Kings (incomplete; some further material in Jeremiah) and the later Chronicles - Nehemiah are in their present form posterior to Nehemiah's time.
The great commentaries exist only for the Posterior Analytics, Physics, De Caelo, De Anima and Metaphysics.
Its posterior faï¿½e is fine.
The Posterior Analytics, on demonstrative syllogism, or science; 5.
21; Posterior Analytics, i.
In the Posterior Analytics the syllogism is brought into decisive connexion with the real by being set within a system in which its function is that of material implication Posterior from principles which are primary, immediate and Analytics.
7 Posterior Analytics, i.
4 Posterior Analytics, ii.
13.6 Posterior Analytics, ii.
6 Posterior Analytics, i.
8 Posterior Analytics, ii.
16 Posterior Analytics, 72a 16 seq.
Posterior Analytics, 77a 26, 76a 37 sqq.
18 Posterior Analytics, ii.
5 Posterior Analytics, ii.
Thus to Aristotle the a priori argument is from law or cause to effect, as opposed to what we call a posteriori (posterior, subsequent, derived), from effect to cause.
In Ireland, Sir William Wilde has assigned their range approximately to the period between the 9th and 16th centuries; while Dr Munro holds that the vast majority of them, both in Ireland and in Scotland, were not only inhabited, but constructed during the Iron Age, and that their period of greatest development was as far posterior to Roman civilization as that of the Swiss Pfahlbauten was anterior to it.
The back of the body is occupied by a crest, called the dorsal fin, consisting of a hollow ridge, the cavity of which is divided into about 250 compartments or fin chambers, into each of which, with the exception of those near the anterior and posterior end of the body, projects a stout pillar composed of characteristic laminar tissue, the fin ray.
New clefts continue to form at the posterior end of the pharynx during the adult life of the animal.
At the level of its posterior end a pair of funnel-shaped pouches of the atrium are produced forwards into the dorsal coelom.
It is the central nervous system, and contains within itself the elements of the brain and spinal marrow of higher forms. The neurochord tapers towards its posterior end, where it is coextensive with the notochord, but ends abruptly in front, some distance behind the tip of the snout.
An important fact to note is that the blastopore is included in this overgrowth of epiblast, so that the neural tube remains for some time in open communication with the archenteron by means of a posterior neurenteric canal.
It is thus possible that the neurenteric canal is due to the conjunction of a posterior neuropore with the blastopore, i.e.
(Adapted from Hatschek.) pc, Praechordal head-cavity of embryo; cc, collar-cavity (first somite); my, mesodermic somites (myocoelomic or archenteric pouches); ch, notochord with the neural tube (neurochord) lying upon it; np, anterior neuropore; ne, position of posterior neurenteric canal.
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.
These include works on the Physica, the Prior and the Posterior Analytics, the Meteorologica, the De anima, the De generatione animalium, the De generatione et interitu and the Metaphysica.
p.d.l., Posterior dorso-lateral.
p.m.d.,Posterior median dorsal.
p.v.l., Posterior ventro-lateral.
The organization of the oyster, as compared with that of a typical lamellibranch such as Anodon, is brought about by the reduction of the anterior part of the body accompanying the loss of the anterior adductor, and the enlargement of the posterior region.
After escaping from the genital aperture they find their way into the infra-branchial part of the mantle cavity of the parent, probably by passing through the suprabranchial chamber to the posterior extremity of the gills, and then being conducted by the inhalent current caused by the cilia of the gills into the infra-branchial chamber.
In Macropus giganteus and its immediate allies, the premolars and sometimes the first molar are shed, so that in old examples only the two posterior molars and the incisors are found in place.
Rezek, Gindely and others have dealt with the history of Bohemia posterior to the year 1526.
Other editions were printed from other versions, all evidently posterior to the original.
The fresh-water Mussels, Anodonta cygnea, Unio pictorum, and Unio margaritiferus belong to the order Eulamellibranchia of Lamellibranch Molluscs, in which the anterior and posterior adductor muscles are equally developed.
of the class, is the possession of a carapace or shell, arising as a dorsal fold of the integument from the posterior margin of the head-region.
7), except that the coalescence does not usually involve the posterior thoracic somites, several of which remain free, though they may be overlapped by the carapace.
4) the abdominal appendages are constantly divided into an anterior group of three natatory " swimmerets " and a posterior group of three limbs used chiefly in jumping or in burrowing.
In most Decapods the " stomach " or dilated portion of the fore-gut is divided into two chambers, a large anterior " cardiac " and a smaller posterior " pyloric."
The most posterior FIG.
The blastopore generally occupies a position corresponding to the posterior end of the body.
In the region of the trunk, in many cases, paired mesoblastic bands are formed, growing in length by the division of teloblastic cells at the posterior end, and becoming segmented into somites.
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.
14), the posterior five or six thoracic somites have their development greatly retarded, and are still represented by a short unsegmented region of the body at a time when the abdominal somites are fully formed and even carry appendages.
At the same time, the tendency to a retardation in the development of the posterior thoracic somites is very general in Malacostracan larvae, and may perhaps be correlated with the f
The right and left margins of the mantle are united ventrally, leaving an anterior and posterior aperture to the mantle cavity.
The shell is narrower at the posterior end and is slightly curved to the dorsal side.
- The animal grows at the anterior end, and therefore the shell at the posterior end is older and thicker.
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.
The living animal buries itself in the sand with only the posterior extremity projecting into the Siphonopodiidae.
o, Orifice leading into po, Posterior orifice of go, Gonad.
The posterior appendix of the mantle.
water, so that the posterior aperture of the mantle cavity is both inhalant and exhalant.
b' Posterior do.
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.
Shell curved with greatest diameter at anterior aperture and diminishing gradually to posterior.
Dentalium: posterior aperture of shell entire, without incision.
Antalis: posterior aperture with short incision.
Fissidentalium: posterior aperture with long fissure on ventral side; abyssal.
Schizodentalium: ventral border of posterior aperture with a series of small holes in a straight line.
The posterior margin of the wing is made to rotate, during the down stroke, in a direction from above downwards and from behind forwards - the anterior margin travelling in an opposite direction and reciprocating.
During the up or return stroke, on the other hand, the posterior margin rotates in a direction from below upwards and from before backwards, so that by a similar but reverse screwing motion the pinion attacks the air from beneath.".
The wing of the bird, like that of the insect, is concavo-convex, and more or less twisted upon itself when extended, so that the anterior or thick margin of the pinion presents a different degree of curvature to that of the posterior or thin margin.
a, b, Crests of the wave; c, d, e, up strokes; x, x, down strokes; f, point corresponding to the anterior margin of the wing, and forming a centre for the downward rotation of the wing (a, g); g, point corresponding to the posterior margin of the wing, and forming a centre for the upward rotation of the wing (d, f).
The wing, during its vibrations, rotates upon two separate centres, the tip rotating round the root of the wing as an axis (short axis of wing), the posterior margin rotating around FIG.
The twisting referred to is partly a vital and partly a mechanical act; - that is, it is occasioned in part by the action of the muscles and in part by the greater resistance experienced from the air by the tip and posterior margin of the wing as compared with the root and anterior margin, - the resistance experienced by the tip and posterior margin causing them to reverse always subsequently to the root and anterior margin, which has the effect of throwing the anterior and posterior margins of the wing into figure-of-8 curves, as shown at figs.
The different parts of the wing, moreover, travel at different degrees of velocity - the tip and posterior margin of the wing always rushing through a much greater space, in a given time, than the root and anterior margin.
Long axis (axis for posterior margin of wing, h, i, j, k, 1).
One naturally inquires why the high speed of wings, and why the progressive increase of speed at their tips and posterior margins?
Thus the tip travels at a higher speed than the root, and the posterior margin than the anterior margin.
Whether, therefore, the air strikes the wings from below, or the wings strike the air from above, the result is the same, - the posterior or flexible margins of the wings yield in an upward direction, and in so doing urge the bird in a horizontal direction."
There are three points in Borelli's argument to which it is necessary to draw attention: (r) the direction of the down stroke: it is stated to be vertically downwards; (2) the construction of the anterior margin of the wing: it is stated to consist of a rigid rod; (3) the function delegated to the posterior margin of the wing: it is said to yield in an upward direction during the down stroke.
the upward bending of the posterior margin of the wing during the down stroke, it is necessary to remark that the statement is true if it means a slight upward bending, but that it is untrue if it means an extensive upward bending.
Marey further states that during the up stroke the wing yields to a corresponding extent in an opposite direction - the posterior margin of the wing, according to him, passing through an angle of go°, plus or minus according to circumstances, every time the wing rises and falls.
That the posterior margin of the wing yields to a slight extent during both the down and up strokes will readily be admitted, alike because of the very delicate and highly elastic properties of the posterior margins of the wing, and because of the comparatively great force employed in its propulsion; but that it does not yield to the extent stated by Marey is a matter of absolute certainty.
If any one watches the horizontal or upward flight of a large bird he will observe that the posterior or flexible margin of the wing never rises during the down stroke to a perceptible extent, so that the under surface of the wing, as a whole, never looks backwards.
He describes two artificial wings, the one composed of a rigid rod and sail - the rod representing the stiff anterior margin of the wing; the sail, which is made of paper bordered with cardboard, the flexible posterior margin.
Carried by the ribbing (the anterior margin of the wing) which lowers itself, the sail or posterior margin of the wing being raised meanwhile by the air, which sets it straight again, the sail will take an intermediate position and incline itself about 45° plus or minus according to circumstances.
o a, Posterior margin of the right wing, consisting of flexible feathers.
b c, Anterior; and f, Posterior margins of the left wing same as the right.
It is of a more or less triangular form, thick at the root and anterior margin, and thin at the tip and posterior margin.
The twisting is most marked at the tip and posterior margin, particularly that half of the posterior margin next the tip. The wing when in action may be divided into two portions by a line running diagonally between the tip of the wing anteriorly and the root of the wing posteriorly.
The tip and posterior parts of the wing are more active than the root and anterior parts, from the fact that the tip and posterior parts (the wing is an eccentric) always travel through greater spaces, in a given time, than the root and anterior parts.
It is not possible to determine with exactitude the precise function discharged by each part of the wing, but experiment tends to show that the tip of the wing elevates, the posterior margin propels, and the root sustains.
x, Root of right wing with ball c d, Posterior margin of dit