3, 4) the interior of the dorsal valve is variously furrowed to receive the lophophore folded in two or more lobes.
Its two lips fusing together at the corners of the mouth are prolonged into the socalled arms. These arms, which together form the lophophore, TV.
The great arm-sinus of each side of the lophophore lies beneath the fold or lip which together with the tentacles forms the ciliated groove in which the mouth opens.
The small arm-sinus runs along the arms of the lophophore at the base of the tentacles, and gives off a blind diverticulum into each of these.
- Diagrammatic section through an arm of the lophophore of Crania.
It is a remarkable fact that in Discinisca, although the vessels to the lophophore are arranged as in other Brachiopods, no trace of a heart or of the posterior vessels has as yet been discovered.
The lophophore and stalk are largely composed of this tissue.
The chief arm-nerve traverses the lophophore, being situated between the great arm-sinus and the base of the lip (figs.
Like the chief armnerve, this strand runs through the lophophore, parallel indeed with the former except near the middle line, where it passes ventrally to the oesophagus.
The lophophore is supplied by yet a third nerve, the under arm-nerve, which is less clearly defined than the others, and resembles a moderate aggregation of the nerve fibrils, which seem everywhere to underlie the ectoderm, and which in a few cases are gathered up into nerves.
The chaetae drop off, and the lophophore is believed to arise from thickenings which appear in the dorsal mantle lobe.
By this time the eyes have disappeared, the four bundles of chaetae have dropped off, and the lophophore has begun to appear as an outgrowth of the dorsal mantle lobe.
Lophophore supported by calcareous loops, &c. [[Families.
Lophophore circular, including both mouth and anus.
Lophophore circular or horseshoe shaped, including the mouth but not the anus.
Gymnolaemata (Allman).- Lophophore circular, with no epistome.
- Lophophore horse-shoe shaped, or in Fredericella circular.
The polypide consists of a "lophophore" bearing a series of ciliated tentacles by which Diatoms and other microscopic bodies are collected as food, of a U-shaped alimentary canal, and of a central nervous system.
The lophophore is a simple circle in all Polyzoa except in the Phylactolaemata, where it typically has the form of a horse shoe outlined by the bases of the tentacles.
At the tip of the introvert the mouth opens, and is surrounded in Sipunculus by a funnel-shaped, ciliated lophophore (figs.
2, 3) the two ends of the lophophore are rolled into spirals.
2) shows: the mouth (m), continuous on either side with the groove between the two series of tentacles; the anus (a), in the middle line, at no great distance from the mouth; a transversely elongated epistome (ep), between the mouth and the anus; and, in the concavity of the lophophore, the apertures of the nephridia (n.o.) which, according to De Selys-Longchamps, open into the two large sensory or glandular "lophophoral organs " the orifices of which are seen at gl.
There is, however, a considerable amount of resemblance between the lophophore of Phoronis australis, with its spirally twisted ends, and that of a typical Brachiopod; nor do the structural details of the adult Brachiopods forbid the view that they may be related to Phoronis.
It will be noticed that the lophophore of Phoronis is, on this assumption, a derivative of the collar just as it is in the Pterobranchia.
On the surface of the funnel-shaped lophophore are numerous ciliated grooves, and each of the tentacles in the tentaculated forms has a similar groove directed towards the mouth.
A so-called heart lies on the dorsal surface of the oesophagus; it is closed behind, but in front it opens into a circumoesophageal ring, which gives off vessels into the lophophore and tentacles.