Siphons or nutritive appendages, from which the order takes its.
The siphons have been compared to the manubrium of a medusa-individual, or to polyps, and hence are sometimes termed gastrozoids.
68, g), present in some genera, especially in Physonectae; similar to the siphons but without a mouth, and purely tactile in function, hence sometimes termed dactylozoids.
In their most primitive form they are seen in Velella as " gonosiphons," which possess mouths like the ordinary sterile siphons and bud free medusae.
A cormidium may contain a single nutritive siphon (" monogastric ") or several siphons (" polygastric ").
Pipes conveying the water of an aqueduct across a valley and following the contour of the sides are sometimes called siphons, though they do not depend on the principle of the above instrument.
Siphons are sometimes used to carry the water over an undulating grade and thereby save the expense of a deep rock cutting.
In the former will be found such things as siphons," Hero's fountain," penny-in-theslot "machines, a fire-engine, a water-organ, and arrangements employing the force of steam.
The solution is removed by ladles or by siphons, and the residue is leached out with boiling water; this removes the sulphates.
The edges of the mantle are united posteriorly except at the anal and branchial apertures, which are placed at the ends of two very short siphons or tubular prolongations of the mantle; the siphons bear a number of short tentacles, and many of these are furnished with eye-spots.
These notches are known in Anodonta as the afferent and efferent siphonal notches respectively, and correspond to the long tube-like afferent inferior and efferent superior " siphons " formed by the mantle in many other Lamellibranchs (fig.
The phenomenon of " concrescence " which we have already had to note as showing itself so importantly in regard to the free edges of the mantle-skirt and the formation of the siphons, is what, above all things, has complicated the structure of the Lamellibranch ctenidium.
Siphons absent or very short.
Callocardiidae.-Siphons present; external gill-plate smaller than the internal; umbones not prominent.
Cyrenellidae.-Two elongated, united, non-retractile siphons; freshwater.
Leptonidae.-Shell thin; no siphons; foot long and byssiferous; marine; hermaphrodite and incubatory.
Cyrenidae.-Two siphons, more or less united, with papillose orifices; pallial line Inj 6 r 6.
Cycladidae.-One siphon or two free siphons with simple orifices; pallial line simple; hermaphrodite, embryos incubated in external gill-plate; freshwater, Cyclas; British.
Rangiidae.-Two short siphons; shell with prominent FIG.
Cardiniidae.-Shell elon removed, and the siphons gated, inequilateral.
Megalodontidae.-Shell 1a, tr, Upper and lower inequilateral, thick; posterior siphons adductor impression on a myo ms, Siphonal muscle of the phorous apophysis.
Pallial suture and no siphons; freshwater; larva a glochidium.
Tellinidae.-External gill-plate directed upwards; siphons separate and elongated; foot with byssus; palps very large; ligament external.
Scrobiculariidae.-External gill-plates directed upwards; siphons separate and excessively long; foot without byssus.
Donacidae.-External gill-plate directed ventrally; siphons separate, of moderate length, anal siphon the longer.
Mesodesmatidae.-External gill-plate directed ventrally; siphons separate and equal.
28, with its foot and siphons expanded.
Two pallial sutures, siphons somewhat elongated and partially or wholly united.
Glaucomyidae.-Siphons very long and united; foot small; shell thin, with deep pallial sinus; fresh or brackish water.
Siphons generally short.
Cardiidae.-Mantle slightly closed; siphons very short surrounded by papillae which often bear eyes; foot very long.
Limnocardiidae.-Siphons very long, united throughout; shell gaping; two adductors; brackish waters.
Tridacnidae.-Mantle closed to a considerable extent; apertures distant from each other; no siphons; a single adductor; shell thick.
Mactridae.-External gill-plate directed ventrally; siphons united, invested by a chitinous sheath; foot long, bent at an angle, without byssus.
Mantle closed to a considerable extent; siphons well developed; gills much folded and frequently prolonged into the branchial siphon.
- Siphons very long and quite separate; foot large; shell oval, elongated, ligament external.
- Siphons united for the greater part of their length, and with a circlet of tentacles near their extremities; foot reduced; shell gaping; ligament internal.
- Shell sub-trigonal, inequivalve; pallial sinus shallow; siphons short, united, completely retractile; foot large, pointed, often byssiferous.
- Mantle extensively closed; a fourth pallial aperture behind the foot; siphons long and united; shell elongated, a spoon-shaped projection for the ligament on each valve.
- Mantle extensively closed, with a small pedal orifice; siphons long, united, covered by a chitinous sheath; gills prolonged into the branchial siphon; foot small; shell gaping.
- Shell thin, gaping widely at the posterior end; anterior adductor much reduced; mantle extensively closed; siphons long, united.
Mantle largely 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 a fourth aperture; siphons long, quite separate, completely retractile and invertible.
- Siphons separate, naked, completely retractile but not invertible.
- Siphons long, united, covered by a chitinous sheath, not completely retractile.
- Mantle with fourth aperture; siphons very long, completely united, naked, incompletely retractile; foot small, with posterior appendage.
- Shell thin, inequivalve, free; ligament internal; siphons very short.
- Shell very inequivalve, solid, with a pallial sinus; siphons short; foot small.