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.
The portion of Carniola belonging to the Karst region presents a great number of caves, subterranean streams, funnels and similar phenomena.
To this pericardial coelom is frequently added a gonocoel enclosing the gonads and the funnels of their ducts.
In Lumbricus the connexion is a little closer; the funnel of the nephridium, in the segments in which the funnels of the gonad ducts are to be developed, persists and is continuous with the gonad duct funnels on their first appearance.
At the least there is no doubt that the genital funnels are developed precisely where the nephridial funnels formerly existed.
If the genital funnels are not wholly or partly formed out of the nephridial funnels they have replaced them.
In the genital segments of Eudrilus the nephridia are present, but the funnels have not been found though they are obvious in other segments.
Here also the genital funnels have either replaced or been formed out of nephridial funnels.
But the funnel is large and thus differs from the funnels of the nephridia in adjoining segments.
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.
The Oligochaeta contrast with the Polychaeta in the general presence of outgrowths of the septa in the genital segments, which are either close to, or actually involve, the gonads, and into which may also open the funnels of the gonad ducts.
These cavities communicate with the exterior through the gonad ducts, which have nothing to do with them, but whose coelomic funnels are taken up by them in the course of their growth.
Nephridia always paired, rarely (Pontobdella) forming a network communicating from segment to segment; lumen of nephridia always intracellular, funnels pervious or impervious.
In Pontobdella and Branchellion the nephridia form a network extending from segment to segment, but there is only one pair of funnels in each segment.
It is remarkable, in view of the spaciousness of the coelom, that the funnels of the latter have not been seen.
Burger) in coelomic spaces close to nephridial funnels, which have, however, no relation to the gonad ducts.
They pass out through short vasa deferentia with internal ciliated funnels, sometimes an enlargement on their course - the seminal vesicles - and a minute external pore situated on the side of the tail.
In the male there are a right and a left protrusible penis in every genital segment, into which opens the nephridium and a sperm-sac. The wide funnels of the nephridia of this region are possibly of coelomic origin.
(3) Portion of (2) enlarged to show atrio-coelomic canals ("brown funnels" of Lankester).
These are the atrial coelomic funnels or brown funnels, so called on account of the characteristic pigmentation of their walls.
There are reasons for supposing that these funnels are vestiges of an ancient excretory system, which has given way by substitution to the excretory tubules described above.
Into this same cloacal chamber open ventrally a pair of ciliated tubes communicating by funnels with the coelom (Nansen and Wheeler); these are possibly nephridia, and excretory in function.
The absence of an apical system of plates; the fact that radial symmetry has not affected the generative organs, as it has in all other recent classes; the welldeveloped muscles of the body-wall, supposed to be directly inherited from some worm-like ancestor; the presence on the inner walls of the body in the family Synaptidae of ciliated funnels, which have been rashly compared to the excretory organs (nephridia) of many worms; the outgrowth from the rectum in other genera of caeca (Cuvierian organs and respiratory trees), which recall the anal glands of the Gephyrean worms; the absence of podia (tube-feet) in many genera, and even of the radial water-vessels in Synaptidae; the absence of that peculiar structure known in other echinoderms by the names "axial organ," "ovoid gland," &c; the simpler form of the larva - all these features have, for good reason or bad, been regarded as primitive.
(3) As in Chaetopoda, coelomic funnels (coelomoducts) may occur right and left After Lankester, Q.
Each nephridium is provided with either one or two funnels which open into the postseptal division of the coelom (ne.f).
Beddard) the funnels of the pronephridia disappear except in the genital segments, where they seem to be actually converted into the genital funnels.