The other extreme end closes, but the invaginated endoderm cells remain in continuity with this extremity of the blastopore, and form the " rectal peduncle " or " pedicle of invagination " of Lankester, although the endoderm cells retain no contact with the middle region of the now closed-up blastopore.
Beecher's division of the Brachiopoda into four orders is based largely on the character of the aperture through which the stalk or pedicle leaves the shell.
The triangular pedicle-opening seen in Orthis, &c., has been named by James Hall and J.
The two plates may meet in the middle line, and leave only a small oval opening near the centre for the pedicle, as in Rhynchonella; or they may meet only near the base of the delthyrium forming the lower boundary of the circular pedicle-opening, as in Terebratula; or the right plate may remain quite distinct from the left plate, as in Terebratella.
The pedicle passes out at right angles to the plane of junction of the valves of the shell; the opening is confined to the ventral valve, and may take the form of a slit, or may be closed by the development of a special plate called the listrium, or by a pseudo-deltidium.
- Diagram of the pedicle-opening of Rhynchonella.
25), no part of the blastopore persists either as mouth or as anus, but the aperture closes - the pedicle of invagination, or narrow neck of the invaginated arch-enteron, becoming the intestine.
Pi, The pedicle of invagination, the future rectum.
From the fact that the bony horn-core of the hollow-horned ruminants first develops as a separate ossification, as do the horns of the giraffe, while the pedicle of the antlers of the deer grow direct from the frontal bone, it has been proposed to place the hollow-horned ruminants (inclusive of the prongbuck) and the giraffes in one group and the deer in another.
The neck is long and curved, and its vertebrae are remarkable for the position of the canal for the transmission of the vertebral artery, which does not perforate the transverse process, but passes obliquely through the anterior part of the pedicle of the arch.
Towards the completion of its growth a more or less prominent ring of bone, termed the burr or coronet, is deposited at its base just above the junction with the pedicle; this ring tending to constrict the blood-vessels, and thus cut off the supply of blood from the antlers...
Pd, The pedicle of the suspensorium continued into cv, the ventral crus of the suspensorium.
Pi, The pedicle of invagina tion, the future rectum.
Pedicle of invagination; its f, The foot.
The ciliated band of the left side of the velar area is indicated by a line extending from v to v; the foot f is seen between the pharynx ph and the pedicle of invagination pi.
This bilobed sac becomes entirely the liver in the adult; the intestine and stomach are formed from the pedicle of invagination, whilst the pharynx, oesophagus and crop form from the stomodaeal invagination ph.