A gizzard is present in a few forms. The buccal cavity is sometimes armed with jaws.
In some Indian and Malay Engystomatids of the genera Callula and Microhyla, the tadpoles are remarkably transparent, and differ markedly in the structure of the buccal apparatus.
This differentiation is not, however, peculiar to the Polychaetes; for in several Oligochaetes the anterior nephridia are of large size, and opening as they do into the buccal cavity clearly play a different function to those which follow.
Parapod.ia hardly projecting; palps of prosomium forming branched gills; no pharynx or eversible buccal region; no septa in thorax, septa in abdomen regularly disposed.
The buccal region is unarmed and not eversible.
Thus, in Octochaetus multiporus a large nephridium opens anteriorly into the buccal cavity, and numerous nephridia in the same worm evacuate their contents into the rectum.
A buccal cavity, a pharynx, an oesophagus and an intestine are always distinguishable.
There are two chitinous jaws in the buccal cavity, a dorsal and a ventral, which are of specially complicated structure in Cirrodrilus.
Bucc, Buccal mass.
- Nervous system of Patella; the visceral loop is lightly shaded; the buccal ganglia are omitted.
- Nervous system of Haliotis; the visceral loop is lightly shaded; the buccal ganglia are omitted.
B, Buccal ganglia.
V, Buccal cavity w, Gonad.
Two pairs of salivary ducts, each leading from a salivary gland, open into the buccal chamber.
The alimentary canal of the Pectinibranchia presents little diversity of character, except in so far as the buccal region is concerned.
(From Gegenbaur, after Jhering.) B, Buccal (suboesophageal) ganglion.
- A, Triton variegation, to show the proboscis or buccal introvert (e) in a state of eversion.
A, Siphonal notch of the shell e, Everted buccal introvert (prooccupied by the siphonal boscis).
Our figure of the nervous system of Aplysia does not give the small pair of buccal ganglia which are, as in all glossophorous Molluscs, present upon the nerves passing from the cerebral region to the odontophore.
T h e buccal nerves and ganglia are omitted.
C, Buccal ganglion.
No buccal appendages or suckers; a very long evaginable proboscis; a quadriradiate terminal branchia.
Of any kind; a short evaginable pharynx, bearing paired conical buccal appendages or " cephalocones."
No branchia; two long and branched buccal appendages.
The last three families constitute the sub-tribe Porostomata, characterized by the reduction of the buccal mass, which is modified into a suctorial apparatus.
59) is sufficiently described in the letterpress attached to it; the pair of buccal ganglia joined by the connectives to the cerebrals are, as in most of our figures, omitted.
The proboscis is not the only organ of locomotion, being assisted by the succeeding segment of the body, the buccal segment or collar.
Not only is the coelom thus subdivided, but the enteron (gut, alimentary canal, digestive tube) itself shows indications of three main subsections in continuity with one another: - (I) proboscis-gut (Eicheldarm, stomochord, vide infra); (2) collar-gut (buccal cavity, throat); (3) truncal gut extending from the collar to the vent.
The paired ctenidia are very greatly developed right and left of the elongated body, and form the most prominent organ of the group. Their function is chiefly not respiratory but nutritive, since it is by the currents produced by their ciliated surface that food-particles are brought to the feebly-developed mouth and buccal cavity.
The alimentary tube consists of three regions: firstly, the anterior buccal mass with the oesophagus, of ectodermic origin, and therefore bearing cuticular structures, namely the jaws and radula; secondly, the mid-gut, of endodermic origin and including the stomach and liver; and, thirdly, the hind-gut or intestine.
In the Gastropoda the muscular tissue of the buccal mass is coloured red by haemoglobin.
The labial commissure supplies only the buccal mass and the oesophagus and stomach.
CHITON, the name 1 given to fairly common littoral animals of rather small size which belong to the phylum Mollusca, and, in the possession of a radula in the buccal cavity, resemble more especially the Gastropoda.
B, buccal mass; m, retractor muscles of the buccal mass; ov, ovary; od, oviduct; i, coils of intestines; ao, aorta; c', left auricle; c, ventricle.
The mouth leads into the buccal cavity, on the ventral side of which opens the radular caecum.
Two pairs of glands open into the buccal cavity, and at the junction of pharynx and oesophagus is another pair called the sugar glands.
The four cords are all connected anteriorly with the cerebral commissure which lies above the buccal mass anteriorly.
The latter bears two ganglion swellings, the buccal ganglia.
B, Buccal ganglia (concerned with the odontophore).
In front of the buccal mass is a median cerebral ganglion.
On the floor of the pharynx or buccal mass is a rudimentary radula, which in many species consists of a single large tooth, bearing two small teeth or a row of teeth.
Two pairs of salivary glands open into the buccal cavity.
- anp, Anterior neural pore; be, rudiment of buccal skeleton; c, cilia; cb, ciliated band; cc, ciliated groove; cm, cilia at margin of mouth; gl, external opening of club-shaped gland; Hn, Hatschek's nephridium; lm, left metapleur; n, notochord; pp, praeoral pit; ps, primary gill-slits, I, 5, and 13; rm, right metapleur showing through.
- For the present, as of old, the true Brachyura are divided into four tribes: Cyclometopa, with arched front as in the common eatable crab; Catometopa, with front bent down as in the land-crabs and the little oyster-crab; Oxyrhyncha, with sharpened beak-like front as in the various spider-crabs; Oxystomata, including the Raninida, and named not from the character of the front but from that of the buccal frame which is usually narrowed forwards.
Buccal mass and radular apparatus are present, but ctenidia are entirely wanting.
The cavity within the head leads into a true buccal cavity situated within the body at the base of the foot.
This buccal sac is provided with a dorsal mandible and a ventral radula.
The buccal cavity contains a sense-organ on the ventral side called the sub-radular organ.
K Gonad., Buccal mass (showing through the mantle).
The buccal mucous membrane will be greyish, brown or black in colour, due to the corrosive effects of the acid.
That all the Arthropoda are to be traced to a common ancestor resembling a Chaetopod worm, but differing from it in having lost its chaetae and in having a prosthomere in front of the mouth (instead of prostomium only) and a pair of hemignaths (mandibles) on the parapodia of the buccal somite.
The second somite is the buccal somite (II, fig.
D, is the neuromere of the second III and IV, Coelom of the-third or buccal somite.
Of these facts is given by saying FP, Rudimentary frontal pro that the Onychophora are " deutercesses perhaps repre ognathous " - that is to say, that senting the prostomial the buccal somite carrying the mantentacles of Polychaeta.
The buccal somite, with its mandibles, is in Hexapoda, as in Crustacea, the fourth: they are tetartognathous.
The adhesion of a greater or less number of somites to the buccal somite posteriorly (opisthomeres) is a matter of importance, but of minor importance, in the theory and history of the Arthropod head.
In Diplopoda two opisthomeres - that is to say, one in addition to the buccal somiteare united by a fusion of their terga with the terga of the prosthomeres.
The two somites following the mandibular or first post-oral or buccal somite carry appendages modified as maxillae.
That the buccal gnathobasic parapodia (the mandibles) were in each of the three grades of prosthomerism only developed after the recession of the mouth and the addition of one, of two, or of three post-oral somites to the prae-oral region had taken place.
On the whole the facts seem to be against this supposition, though we need not suppose that the gnathobase was very large or the rami undeveloped in the buccal parapodia which were destined to lose their mandibular features and pass in front of the mouth.
The buccal glands are arranged in two ?., rows parallel with the molar teeth.