These vessels are the nitrogenous excretory organs.
The excretory organs, the 5.
The excretory system is epiblastic in its origin.
The excretory tubes, the nervous system, and the parenchyma and integument are continuous from one end of the worm to the other.
The excretory system is highly developed and opens at the posterior extremity by a paired muscular bladder.
The coelom is lined throughout by cells, which upon the intestine become large and loaded with excretory granules, and are known as chloragogen cells.
It is not quite certain whether these are to be regarded as the remnant of an earlier excretory system, replaced among the Oligochaeta by the subsequently developed paired structures, or whether these "head kidneys" are the first pair of nephridia precociously developed.
Among the Megascolicidae, however, which in number of genera and species nearly equals the remaining families taken together, another form of the excretory system occurs.
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.
The nephridia or excretory 14.
It must be pointed out that the presence or absence of such renal excretory tubes opening into the intestine appears to be a question FIG.
Further, it is pointed out by Korschelt and Heider that the hinder portion of the gut frequently acts in Arthropoda as an organ of nitrogenous excretion in the absence of any special excretory tubules, and that the production of such caeca from its surface in separate lines of descent does not involve any elaborate or unlikely process of growth.
The excretory system consists of peculiar cells, each of which bears several"flames" or bunches of synchronously vibrating cilia.
B, head showing the suckers, proboscides and excretory canals; X 25.
The terminal or first-formed proglottis is sterile, and contains the primitive and (except in a few genera) the only excretory pore.
The excretory pore is terminal and posterior in endoparasitic forms: paired, anterior and dorsal in the ectoparasitic class.
2, D) and canaliculi of the excretory system as in Turbellaria, others again muscle-cells.
The excretory system opens to the exterior by a pair of dorsal pores at the level of the pharynx.
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.
40); in Geryonia, however, it remains double, and the centripetal canals arise by parting of the two layers; (4) excretory endoderm, lining pores at the margin of the umbrella, occurring in certain Leptomedusae as socalled " marginal tubercles," opening, on the one hand, into the ring-canal and, on the other hand, to the exterior by " marginal funnels," which debouch into the sub-umbral cavity above the velum.
In some Leptomedusae excretory " marginal tubercles " are developed on the ring-canal.
- Excretory organs which are undisputed nephridia are practically universal among the Oligochaeta, Hirudinea and Archiannelida, and occur in many Polychaeta.
The Polychaeta, however, present us with another form of nephridium seen, for example, in Arenicola, where a large funnel leads into a short and wide excretory tube whose lumen is intercellular.
It is not clear, for example, to which category it is necessary to refer the excretory organs of Arenicola, or Polynoe.
Thus Nereis among the latter worms, from the resemblance which its excretory system bears to that of the Oligochaeta, may be made the starting-point of a series.
The nervous system is, however, not segmented, and the excretory system is continuous throughout the worm.
The mass of the body consists of richly branched stellate cells - the mesenchyma - and imbedded in this plasmic tissue are the nervous, excretory, muscular and generative organs.
When taken internally it is both a secretory and an excretory cholagogue, but so irritant and powerful that its use in cases of jaundice is generally undesirable.
The relation ~ of the laticiferous tissue to the assimi I lating cells under which they often end, and the fact that where this tissue is / richly developed the conducting paren ~ chyma of the bundles, and sometimes also 4 the sieve-tubes, are poorly developed, as well as various other facts, point to the conclusion that the laticiferous system has an important function in conducting plastic substances, in addition to acting as an excretory reservoir.
The excretory (malpighian) tubes are few in number, either four or six.
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.
The tips of these tufts enclose a flamecell similar to those found in Platyhelminths, &c., and these probably function as excretory organs.
They are lined by cells charged with a yellow or brown pigment, and besides their excretory functions they act as ducts through which the reproductive cells leave the body.
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.
Scorpio is here provided with a single or double pair of renal excretory tubes, which have been identified by earlier authors with the Malpighian tubes of the Hexapod and Myriapod insects.
Limulus agrees with the majority of the Crustacea in being destitute of renal excretory caeca or tubes opening into the hinder part of the gut.
(From Lankester, "Limulus an Arachnid.) of adaptation to the changed physiological conditions of respiration, and not of morphological significance, since a pair of renal excretory tubes of this nature is found in certain Amphipod Crustacea (Talorchestia, &c.) which have abandoned a purely aquatic life.
In fact it is not possible to maintain that the renal excretory tubes of the gut are of one common origin in the Arthropoda.
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.
A well-developed cellular parenchyma forms a matrix in which the muscular, excretory and generative organs are imbedded.
In the remainder the segmentation involves primarily the genitalia and includes the integument, muscles and part of the excretory system.
Each cansists of an eversible hollow tentacle provided with hooklets and capable of introversion within a mem The excretory organs consist of flame-cells, richly convoluted canaliculi, and a pair of longitudinal canals leading to the exterior by one or more pores.
An excretory system develops, opening at FIG.
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.
D, a flame-cell from the excretory apparatus, highly magnified (from Fraipont).
It has been ascertained that the nephridia of Oligochaeta are preceded in the embryo by a pair of delicate and sinuous tubes, also found in the Hirudinea and Polychaeta, which are larval excretory organs.
- Diagram conveying the digested food-products all over of the circulatory the body, and the excretory products to the apparatus in the annephridia, and doubtless it serves at times to tenor body-region of assist in the extension and retraction of parts a Metanemertine.
- Part of the few exceptions (Tetrastemma herma- excretory system lying phrodilica, Marion).
The Priapuloidea are dioecious, and their male and female organs, which are one with the excretory organs, consist of a pair of branching tufts, each of which opens to the exterior on one side of the anus.
Pectinibranchia.-In this order there is no longer any trace of bilateral symmetry in the circulatory, respiratory and excretory organs, the topographically right half of the pallial complex having completely disappeared, except the right kidney, which is FIG.
The possession of a variable number of excretory tubes (Malpighian tubes), which are developed as outgrowths of the hind-gut and pour their excretion into the intestine,is also a distinctive character of the Hexapoda.