Ctenidium Sentence Examples

It will be remembered that, according to Spengel, the osphradium of mollusca is definitely and intimately related to the gill-plume or ctenidium, being always placed near the base of that organ; further, Spengel has shown that the nerve-supply of this olfactory organ is always derived from the visceral loop. Accord ingly, the nerve-supply FIG.

Spire of shell much reduced; a single ctenidium.

No ctenidium, but a pulmonary cavity; heart with a single auricle, not traversed by the rectum.

This organ has, without reason, been supposed to represent the second ctenidium of the typical mollusc, which it cannot do on account of its position.

To the left of the ctenidium a pulmonary sac, separated from it by an incomplete septum, am phibious.

Mantle with two posterior appendages; ctenidium large and capable of protrusion from pallial cavity.

Where the modification is carried to its extreme degree, not only the shell but the pallial cavity, ctenidium and visceral hump disappear, and the body acquires a simple elongated form and a secondary external symmetry, as in Pterotrachaea and in Doris, Eolis, and other Nudibranchia.

The heart lies in front of, instead of to the side of, the attachment of the ctenidium - hence Opisthobranchia as opposed to " Prosobranchia," which correspond to the Streptoneura.

Many Opisthobranchia have by a process of atrophy lost the typical ctenidium and the mantleskirt, and have developed other organs in their place.

The gill-plume,which in A plysia is the typicalMolluscan ctenidium, is seen in fig.

The whole surface of the body becomes greatly modified in those Nudibranchiate forms which have lost, not only the shell, but also the ctenidium.

There is a ctenidium, except in some Thecosomata and Gymnosomata, and an osphradium.

The pallial cavity is always well developed, and contains the ctenidium, at least in part; ctenidium, except in Lophocercidae, of folded type.

Cephalic shield continuous with dorsal integument; no shell; ctenidium projecting from mantle cavity.

Foot without parapodia; no pallial cavity, but always a single ctenidium situated on the right side between mantle and foot.

Shell external and conical; anterior tentacles form a frontal veil; ctenidium extending only over right side; a distinct osphradium.

Shell external, conical, much flattened; anterior tentacles very small, and situated with the mouth in a notch of the foot below the head; ctenidium very large.

Pulmonata are widely distinguished from a small number of Streptoneura at one time associated with them on account of their mantle-chamber being converted, as in Pulmonata, into a lung, and the ctenidium or branchial plume aborted.

The position of the osphradium corresponds more or less closely with that of the vanished right ctenidium, with which it is normally associated.

We thus expose the plough-like foot (I), the two left labial tentacles, and the two left gill-plates or left ctenidium.

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.

The Molluscan ctenidium is typically a plume like structure, consisting of a vascular axis, on each side of which is set a row of numerous lamelliform or filamentous processes.

The filaments of the gill (ctenidium) of Mytilus and Arca thus form two closely set rows which depend from the axis of the gill like two parallel plates.

As the axis of the ctenidium lies by the side of the body, and is very frequently connate with the body, as so often happens in Gastropods also, we find it convenient to speak of the two plate-like structures formed on each ctenidial axis as the outer and the inner gill-plate; each of these is composed of two lamellae, an outer (the reflected) and an adaxial in the case of the outer gill plate, and an adaxial and an inner (the reflected) in the case of the inner gill-plate.

Section across the axis of a ctenidium with a pair of plates - flattened and shortened filaments - attached.

Although the structured of the ctenidium is thus highly complicated in Anodonta, it is yet more so in some of the siphonate genera of Lamellibranchs.

Other points in the modification of the typical ctenidium must be noted in order to understand the ctenidium of Anodonta.

The axis of each ctenidium, right and left, starts from a point well forward FIG.

If we were to make a vertical section across the long axis of a Lamellibranch which had the axis of its ctenidium free from its origin onwards, we should find such relations as are shown in the diagram fig.

The axis of the ctenidium is seen to be adherent to, or fused by concrescence with, the body-wall, and moreover on each side the outer lamella of the outer gill-plate is fused to the mantle, whilst the inner lamella of the inner gill-plate is fused to the foot.

It is important, because such a concrescence is by no means universal, and does not occur, for example, in Mytilus or in Arca; further, because when its occurrence is once appreciated, the reduction of the gill-plates of Anodonta to the plume-type of the simplest ctenidium presents no difficulty; and, lastly, it has importance in reference to its physiological significance.

Portion of the axis of the left ctenidium which is fused with the base of the foot, the two dotted lines indicating the origins of the two rows of gill-filaments.

The afferent vessel of the' ctenidium receives blood from the vena cava or principal blood-sinus of the body, the efferent vessel opens into the auricle of its own side.

Near the base of the ctenidium is a patch of sensory epithelium innervated from the branchial nerve, forming a sense-organ called the osphradium, whose function is to test the water entering the branchial cavity.

Each auricle forms the terminal enlargement of the efferent vein of the ctenidium of its own side.

Each gill has the structure of a typical molluscan ctenidium, consisting of an axis bearing an anterior and posterior row of filaments or lamellae.

Shell with very low spire, without umbilicus, internal partitions frequently absorbed; a single ctenidium; a cephalic penis present.

The " introvert " in these Gastropods is not the pharynx The ctenidium is monopectinate and attached to the mantle along as in the Chaetopod worms, but a prae-oral structure, its apical limit being formed by the true lips and jaws, whilst the apical limit of the Chaetopod's introvert is formed by the jaws placed at the junction of pharynx and oesophagus, so that the Chaetopod's introvert is part of the stomodaeum or fore-gut, whilst that of the Gastropod is external to the alimentary canal altogether, being in front of the mouth, not behind it, as is the Chaetopod's.

No ctenidium, pallial cavity transformed into a lung; aperture of shell circular; terrestrial.

The ctenidium is atrophied, and the edge of the mantle-skirt is fused to the dorsal integument by concrescence, except at one point which forms the aperture of the mantle-chamber, thus converted into a nearly closed sac. Air is admitted to this sac for respiratory and hydrostatic purposes, and it thus becomes a lung.