This accessory pore is not of uniform significance.
Uterine pore absent.
The most important of these opens by the ventral pedal pore, situated in the median line in the anterior half of the foot.
In these, the male organs ripen before the ova and spermatozoa may pass into the uterus before the external pore is formed (Looss).
Thus, among the Oligochaeta there are often a series of dorsal pores, or a single head pore, present also among the Polychaeta (in Ammochares).
Next the pit closes up to form a vesicle with a pore, and so gives rise to the pneumatophore.
A, Arrow from proboscis-cavity (pc) passing to left of peri cardium (per) and out through proboscis pore-canal.
The excretory pore is terminal and posterior in endoparasitic forms: paired, anterior and dorsal in the ectoparasitic class.
Even his wit and knowledge of the world were spoiled, and his affected gaiety was touched with sadness, by the odour of falsehood which escaped through every pore of his body."
1, T), which open and close the pore according to the need for transpiration.
B, Sole of the foot of Pyrula tuba, to show a, the pore usually said to be " aquiferous " but probably the orifice of a gland; b, median line of foot.
The common genital pore (male and female).
It is within the bounds of possibility that Tornaria actually does indicate a remote affinity on the part of the Enteropneusta to the Echinoderms, not only on account of its external form, but also by reason of the possession of a dorsal water-pore communicating with the anterior body-cavity.
In 1900 it was shown that the coxal gland of Limulus is provided with a very delicate thin-walled coiled duct which opens, even in the adult condition, by a minute pore on the coxa of the fifth leg (Patten and Hazen, 13A).
These cavities are completely roofed by a layer of cells; in the centre of the roof is a pore surrounded by a ring of special cells.
In this stage the body is composed of two layers, ectoderm (d) externally, and endoderm (c) internally, surrounding a central cavity, the archenteron (b), which communicates with the exterior by a pore (a), the blastopore.
If the coenosteum of Millepora be broken across, each pore-canal (perhaps better termed a polypcanal) is seen to be interrupted by a series of transverse partitions, representing successive periods of growth with separation from the underlying dead portions.
The orifice of invagination forms a pore which may be closed up or may form a protruding duct or funnel.
The same arrangement is found in some other Polychaetes; for instance, in Sabellaria there is a single pair of large anterior nephridia, which open by a common pore, followed after an interval by large-funnelled and short nephridia.
A conical, thorn-like projection from the base of the pore, sometimes found also in dactylopores; sessile gonophores.
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.
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.
There are reasons for supposing that the truncal coelom was at one time provided with pore-canals, but supposed vestiges of these structures have only been described for one genus, Spengelia,in which they lie near the anterior end of the truncal coelom.
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.
Besides the wider vertical pore-canals and the narrower, FIG.
Hence the cavity of the air-sack is equivalent to a sub-umbral cavity in which no manubrium is formed, and the pore or orifice of invagination would represent the margin of the umbrella.
This arrangement is a method of checking transpiration by creating a still atmosphere above the pore of the stoma, so that water vapour collects in it and diminishes the further outflow of vapour.
Ray Lankester to the members of a series of tubes, proved in some cases to be excretory in nature, which exist typically to the number of a single pair in most of the segments of the Chaetopod body, and open each by a ciliated orifice into the coelom on the one hand, and by a pore on to the exterior of the body on the other.
There are no setae and apparently only two pairs of nephridia, of which the anterior pair open commonly by a common pore on the third segment after the head, whose segments have not been accurately enumerated.
The proboscis-pores are highly variable, and frequently only one is present, that on the left side; sometimes the pore-canals of the proboscis unite to open by a common median orifice, and sometimes their communication with the probosciscoelom appears to be occluded, and finally the pore-canals may be quite vestigial.
C, arrow intended to pass from 1st gill-pouch through collar pore-canal into collar-coelom (cc).
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.
Under such conditions each particle of soil is surrounded by a thin film of water and in the pore-space air can freely circulate.
Both male and female gonoducts open through acornmon atrium to the exterior by tkis pore, but in three bisexual genera the male and female ducts are developed in separate individuals (Bilharzia, Didymozoon, Koellikeria).
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.
Jullien believed that this pore opens into the tentacle-sheath, but it appears probable that it really communicates with the compensation-sac and not with the tentaclesheath.
Our knowledge of Lanfranc's polemics is chiefly derived from the tract De cor pore et sanguine Domini which he wrote many years later (after 1079) when Berengar had been finally condemned.
This is the case in " puddled " clays, but in ordinary clay soils the excessively minute particles of which they largely consist tend to form groups of comparatively large composite grains and it is in such natural soils that the pore-space is largest.
The mouth may be a simple, circular pore at the extremity of the manubrium, or by folding of the edges it may become square or shaped like a Maltese cross, with four corners and four lips.
The proportional amount of these materials in a sandy soil on the Bagshot beds and a stiff Oxford clay is given below: - The pore-space within the soil, i.e.
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.
Where the soil grains are quite free from each other the smaller grains tend to fill up the spaces between the larger ones; hence it might be concluded that in clays the amount of pore-space would be less than in coarser sands.
These cells are f - - imbedded in the peri pheral parenchyma, E"- and lead into convo luted excretory tubes _ that form an anasto- - mosis opening to the exterior by a pore at the " hinder " end of the body.
Far from the genital pore a glandular c, Spermatheca.
It seems likely that the coelomic pore-canals were originally excretory organs, but in the existing Enteropneusta the pore-canals (especially the collar canals) have, as we have seen, acquired new functions or become vestigial, and the function of excretion is now mainly accomplished by a structure peculiar to the Enteropneusta called the glomerulus, a vascular complex placed on either side of the anterior portion of the stomochord, projecting into the proboscis-coelom.
(Xioo.) reproductive system; C, Cirrus; H, hooks on the ventral sucker; I, small piece of the intestine to show its connexion with the reproductive organs by the narrow duct that passes from it to the union of the vaginae; M, mouth; 0, ovary; S, oral sucker; SC, sucker; SH, shell-gland; T, Testis; U, uterus; V, vaginal pore; Y, yolkgland.
It is to be noted that the Hirudinea differ from the Oligochaeta in that the male pore is in advance of the gonads (except in Acanthobdella, which here, as in so many points, approximates to the Oligochaeta), whereas in Oligochaeta that pore is behind the gonads (again with an exception, Aliurus).
When the pore-space of the soil is filled with water it becomes water-logged and few plants can effect absorption by their roots under such conditions.