from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any small columnlike structure in various plants and animals, often forming the central axis of development for the organism or an anatomical structure.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any of various small structures in plants or animals that are columnar in shape.
- n. The skin at the end of the septum which separates the nostrils.
- n. In birds, reptiles, and amphibians, the small bone which carries vibration from the tympanum to the inner ear.
- n. In gastropods, the structure at the center of the whorls of the shell.
- n. The structure at the center of the calyx where the septa join together.
- n. The central sterile portion of the sporangium in various fungi.
- n. A rod-shaped reinforcing element of the sexine layer of a pollen grain.
There is a central support, called a columella, that runs right through the middle of the shell which gives it strength and provides a point of attachment for the soft parts of the animal.
The assumption commonly made is that vibrations in the water or air by direct contact cause the tympanic membrane to vibrate; this in turn causes a movement of the columella, which is transmitted to the perilymphatic fluid of the inner ear.
[Tracing the development of the columella was a long business, but it grew clearer as young frogs of various ages were examined.] "Don't be aggravated with yourself," [he writes to Parker in July,] "it's tough work, this here Frog."
Such a rod is called a columella; it goes all the way through the center of the shell.
From the septum grows a club-shaped mass of protoplasm -- "columella"
It was carried by wrapping your fingers around the columella and putting your thumb through a neat hole chipped out of the body whorl.
Quoting from Hyman [italics mine]:In [Helix pomatia] the [columellar] muscle, after leaving its origin on the columella, forks into right and left parts, of which the smaller right part sends a branch into each tentacle on that side and then loses itself in the tissues of the foot.
But the shell of D. cronkhitei is not keeled, while D. patulus has a small tooth inside the aperture on the columella that is missing in the Montreal shells.
Dodonaea microzyga, F.M. Somewhat viscid, almost glabrous; leaves with 1 to 2 pairs of small obovate-cuneate leaflets; in front rounded, or truncate, or retuse, or sometimes 3-toothed, flat at the margin; rachis dilated; fruit-bearing pedicels solitary; capsules 3 to 4-celled; valves cymbeo-semiorbicular, all around broadly winged; the wing rounded-blunt on both extremities; dissepiments persistent with the columella.
A fine, solid, brown species, generally more or less eroded, and with a peculiarly strongly plicate columella.
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