The water is expelled from the branchial chambers by one or two tubes opening by one orifice in most Batrachians.
Third visceral or first branchial arch.
The gill-lamellae of Patella are processes of the mantle comparable with the plait-like folds often observed on the roof of the branchial chamber in other Gastropoda (e.g.
In these, as in Patella, the typical ctenidia are aborted, and the branchial function is assumed by close-set lamelliform processes arranged in a series beneath the mantle-skirt on either side of the foot.
4, d, the large branchial vein of Patella bringing blood from the gill-series to the heart is seen; where it crosses the series of lamellae there is a short interval devoid of lamellae.
The heart in Patella consists of a single auricle (not two as in Haliotis and Fissurella) and a ventricle; the former receives the blood from the branchial vein, the latter distributes it through a large aorta which soon leads into irregular blood-lacunae.
Br.a, Branchial advehent vessel (artery).
Br.v, Branchial efferent vessel (vein).
20, will serve to exhibit the disposition of viscera which prevails in the group. The branchial chamber formed by the mantle-skirt overhanging the head has been exposed by cutting along a line extending backward from the letters vd to the base of the columella muscle mc, and the whole roof of the chamber thus detached from the right side of the animal's neck has been thrown over to the left, showing the organs which lie upon the roof.
The surface of the neck is covered by integument forming the floor of the branchial cavity.
Near this and less advanced into the branchial chamber is the single renal organ or nephridium r with its opening to the exterior r'.
It corresponds to the right of the two primitive ctenidia in the untwisted archaic condition of the molluscan body, and does not project freely into the branchial cavity, but its axis is attached (by concrescence) to the mantle-skirt (roof of the branchial chamber).
The Pectinibranchia the pedal nerves are br, Ctenidium (branchial distinctly nerves given off from the pedal plume).
This is a groove, the edges of which are raised and ciliated, lying near the branchial plume in the genera which possess that organ, whilst in Firoloida, which has no branchial plume, the osphradium occupies a corresponding position.
Shell turriculated, with carinated br, Ctenidium (branchial whorls, the carinae tuberculated or plume).
All exto the roof of the branchial tinct.
Br, Branchial plume (ctenidium).
39 projecting from the branchial sub-pallial space.
The ctenidium (branchial plume).
Pharynx suctorial; no radula; branchial rosette on the dorsal surface, above the mantle-border.
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.
Visceral mass and shell conical; tentacles atrophied; head expanded; genital apertures contiguous; marine animals, with an aquatic pallial cavity containing secondary branchial laminae.
The branchial bars which constitute the borders of the clefts are of two kinds: - (i) Septal bars between two contiguous clefts, corresponding to the primary bars in Amphioxus; (2) Tongue bars.
The gill-slits may be stated briefly as follows: - (a) the presence of two kinds of branchial bars in all species and also of small cross bars (synapticula) in many species; (s) numerous gill slits, from forty to more 1 - _ than a hundred pairs; (y) the addition of new gill-slits by fresh perforation at the posterior end of the pharynx throughout life.
- Structure of branchial region.
They occur in the branchial region, and also extend to a variable distance behind it.
In exceptional cases they are either confined to the branchial region or excluded from it.
When they are arranged in uniserial or biserial rows the genital ducts open into or near the branchial grooves in the region of the pharynx and in a corresponding position in the post-branchial region.
An important feature is the occurrence in some species (Ptychoderidae) of paired longitudinal pleural or lateral folds of the body which are mobile, and can be approximated at their free edges so as to close in the dorsal surface, embracing both the median dorsal nerve-tract and the branchial grooves with the gill-pores, so as to form a temporary peri-branchial and medullary tube, open behind where the folds cease.
VIII, The pectens of Scorpio and the first branchial plate of Limulus.
IX, The first pair of lung-books of Scorpio and the second branchial plate of Limulus.
The chief points in which they vary are - (1) in the structure of the ctenidia or branchial plates; (2) in the presence of one or of two chief muscles, the fibres of which run across the animal's body from one valve of the shell to the other (adductors); (3) in the greater or less elaboration of the posterior portion of the mantle-skirt so as to form a pair of tubes, by one of which water is introduced into the sub-pallial chamber, whilst by the other it is expelled; (4) in the perfect or deficient symmetry of the two valves of the shell and the connected soft parts, as compared with one another; (5) in the development of the foot as a disk-like crawling organ (Arca, Nucula, Pectunculus, Trigonia, Lepton, Galeomma), as a simple plough-like or tongueshaped organ (Unionidae, &c.), as a re-curved saltatory organ (Cardium, &c.), as a long burrowing cylinder (Solenidae, &c.), or its partial (Mytilacea) or even complete abortion (Ostraeacea).
A second closely-allied genus of this family is Pseudobranchus, differing in having a single branchial aperture on each side instead of three, and only three fingers.
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.
To these succeed eight pairs of foliaceous branchial appendages on the front division of the body, followed on the hind division by four pairs of powerful bifurcate swimming feet and two rudimentary pairs, the number, though not the nature, of these appendages being malacostracan.
There are also now two more genera, Paranebalia (Claus, 1880), in which the branchial feet are much longer than in Nebalia, and Nebaliopsis (Sars, 1887), in which they are much shorter.
The constituents of the last have often been classed as Copepoda, and among the Branchiopods must be regarded as aberrant, since the "branchial tail " implied in the name has no feet, and the actual feet are by no means obviously branchial.
Respiration is conducted by the general surface, by the branchial lamina (external branch) of the feet, and the vesicular appendage (when present) at the base of this branch.
The former, with the feet for the most part concealed by the carapace, is subdivided into two tribes, the Ctenopoda, or " comb-feet," in which the six pairs of similar feet, all branchial and nonprehensile, are furnished with setae arranged like the teeth of a comb, and the Anomopoda, or " variety-feet," in which the front feet differ from the rest by being more or less prehensile, without branchial laminae.
3), remarkable for seven pairs of long branchial leaves which fold over the hinder extremity of the animal, and the Sarsiellidae, still somewhat obscure, besides adding the Rutidermatidae, knowledge of which is based on skilful maceration of minute and long-dried specimens.
In these the furcal branches are linear or rudimentary, the shell is without rostral sinus, and, besides distinguishing characters of the second 2ntennae, they have always a branchial plate well developed on the first maxillae, which is inconstant in the other tribe.
BR, Seven branchial leaves.