Whitman the entire nephridial system (in the leech Clepsine) is formed by the differentiation of a continuous epiblastic band on each side.
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.
Here again the nephridial funnel seems to have been converted into or certainly replaced by a secondarily developed funnel.
The nephridia of the Polychaeta have been generally dealt with above in considering the nephridial system of the Chaetopoda as a whole.
I more comp complicated in the In all the figures the nephridial pores are indicated by dots and the setae by larger forms than in the strokes.
It is further noticeable that in Rhynchelmis the covering of vesicular cells which clothes the drainpipe cells of the adult nephridium is cut off from the nephridial cells themselves and is not a peritoneal layer surrounding the nephridium.
Burger) in coelomic spaces close to nephridial funnels, which have, however, no relation to the gonad ducts.
A pair of coiled nephridial tubes (n) formed of a file of perforated `' drain-pipe "cells, with ciliated tag-like" flame "cells (f), open into a contractile bladder (bl), FIG.
A pair of genital apertures, connected by genital ducts with the paired gonads, are found right and left near the nephridial pores, except in a few cases where the genital duct joins that of the renal organ (Spondylus).
In the same figure the free part of the inner lamella of the inner gill-plate resting on the foot is marked z, whilst the attached parjt - the most anterior - has been snipped with scissors so as to show the genital and nephridial apertures x and y.
N, Nephridial aperture.
The genital duct opens by a pore into the urino-genital groove of the oyster (the same arrangement being repeated on each side of the body) close to but distinct from the aperture of the nephridial canal.
Reflected portion of the nephridial stem.
N.o., Nephridial surface.
N.o., Nephridial opening.
Ne.f., Larger nephridial funnel.
The internal vesicle is already indicated, and is shown in the diagram by the thinner black line: I, gut; 2, somite; 2', nephridial part of coelom; 3, haemocoele; 3', part of haemocoele which will form the heart - the part of the haemocoele on each side of this will form the pericardium; 4, nerve-cord; 4, slime glands.
A and feet with two primary papillae on the anterior side and one on the posterior side; outer jaw with one minor tooth at the base of the main tooth, inner jaw with no interval between the large tooth and the series of small ones; last fully developed leg of the male with enlarged crural gland opening on a large papilla placed on its ventral surface; coxal organs absent; the nephridial openings of the 4th and 5th pairs of legs are placed in the proximal spinous pad.
P. tholloni, Bouvier, (Equatorial West Africa [Gaboon]), shows some neotropical features; there are 24 to 25 pairs of legs, the genital opening is between the penultimate legs, and though there are only three spinous pads the nephridial openings of the 4th and 5th legs are proximal to the 3rd pad, coxal organs are present, and the jaws are of the neotropical type; the oviducts have receptacula seminis.
- With 22 to 24 pairs of claw-bearing legs, with three spinous pads on the legs, and nephridial openings of legs 4 and 5 (sometimes of 6 also) on the proximal pad; feet with one primary papilla on the anterior, one on the posterior side, and one on the dorsal side (median or submedian); outer jaw with a minor tooth, inner jaw without diastema; crural glands absent; well-developed coxal organs absent.
With 23 to 25 pairs of claw-bearing legs, four spinous pads on the legs, and nephridial openings of legs 4 and 5 in the middle of the proximal pad or on its proximal side; feet with two primary papillae, one anterior and one posterior; outer jaw with two, inner jaw with two or three minor teeth at the base of the main tooth, separated by a diastema from the row of small teeth; crural glands present in the male only, in the two pairs of legs preceding the generative opening; coxal glands present.
With 14, 15 or 16 pairs of claw-bearing ambulatory legs, with three spinous pads on the legs, and nephridial opening of the 4th and 5th legs on the proximal pad; feet with one anterior, one posterior and one dorsal primary papilla; inner jaw without diastema, outer with or without a minor tooth.
- With three to five spinous pads on the legs, nephridial opening of the 4th and 5th legs usually proximal to the 3rd pad, and feet either with two primary papillae on the anterior side and one on the posterior, or with two on the anterior and two on the posterior; outer jaw with small minor tooth or teeth at the base of the main tooth, inner jaw with diastema.
Those which inhabit the high plateaus or Pacific slope of the Andes; in these there are 4 (sometimes 5) pedal papillae, and the nephridial openings of the 4th and 5th legs are on the third pad; and (2) the Caribbean species, viz.
The remaining neotropical species, in which there are 3 papillae on the foot and the nephridial openings of the 4th and 5th legs are between the 3rd and 4th pads.