notochord

Definitions

  • WordNet 3.6
    • n notochord a flexible rodlike structure that forms the supporting axis of the body in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates
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Webster's Revised Unabridged Dictionary
    • n Notochord (Anat) An elastic cartilagelike rod which is developed beneath the medullary groove in the vertebrate embryo, and constitutes the primitive axial skeleton around which the centra of the vertebræ and the posterior part of the base of the skull are developed; the chorda dorsalis. See Illust. of Ectoderm.
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Century Dictionary and Cyclopedia
    • n notochord The chorda dorsalis or primitive backbone: a fibrocellular or cartilaginous rod-like structure which is developed in vertebrates as the basis of the future spinal column, and about which the bodies of the future vertebræ are formed. It is one of the earliest embryonic structures, and persists throughout life in many of the lower vertebrates, which are on this account called notochordal; but in most cases it is soon absorbed and replaced by a definite cartilaginous or bony spinal column. The soft pulpy substance which may be seen filling in the cupped ends of the vertebrw of a fish, as brought to the table, is a part or the remains of the notochord. Anteriorly, in skulled vertebrates, the notochord runs into the base of the skull as far as the pituitary fossa. (see parachordal.) The caudal division of a notochord is often called urochord. Such a structure is characteristic of tunicates or ascidians, called on this account Urochorda, and approximated to or included among vertebrates. (See Appendiculariidæ.) A sort of notochord occurring in the acorn-worms has caused them to be named Hemichorda. (See Balanoglossus and Enteropneusta.) The lancelets are named Cephalochorda with reference to the extension of this structure into the head. See Chordata, and cuts under Pharyngobranchii, chondrocranium, Lepidosiren, and visceral.
    • n notochord A vestigial structure, representing a very ancient form of alimentary canal not in itself a part of the skeleton.
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Chambers's Twentieth Century Dictionary
    • n Notochord nō′tō-kord a simple cellular rod, the basis of the future spinal column, persisting throughout life in many lower vertebrates, as the amphioxus, &c
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Etymology

Webster's Revised Unabridged Dictionary
Gr. nw^ton the back + E. chord,
Chambers's Twentieth Century Dictionary
Gr. nōtos, the back, chordē, a string.

Usage

In literature:

But where did the notochord come from?
"The Whence and the Whither of Man" by John Mason Tyler
The notochord alone is common to both.
"Thomas Henry Huxley; A Sketch Of His Life And Work" by P. Chalmers Mitchell
They have no backbone in the strict sense, but they have this notochord.
"The Outline of Science, Vol. 1 (of 4)" by J. Arthur Thomson
Now the brain capsule, like the sheath of the spinal cord, is a development from the outer sheath of the notochord.
"Form and Function" by E. S. (Edward Stuart) Russell
The microscope shows that these animals have notochords, nervous systems, and ganglia, or brains.
"The Dawn of Reason" by James Weir
Describe the notochord of amphioxus, and point out its differences from the vertebrate notochord.
"Text Book of Biology, Part 1: Vertebrata" by H. G. Wells
It presents, however, a rudimentary backbone, in the form of what is called a notochord.
"Darwin, and After Darwin (Vol. 1 and 3, of 3)" by George John Romanes
The notochordal canal measures 2.8 mm.
"A New Order of Fishlike Amphibia From the Pennsylvanian of Kansas" by Theodore H. Eaton
The lancelet has a spinal cord enclosed in a half-gristly canal (the notochord).
"Degeneracy" by Eugene S. Talbot
He reared gastrulae and older embryos with notochord and nerve-tube, which were perfect and normal, except in size.
"The Biological Problem of To-day" by Oscar Hertwig
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In news:

Abstract Chordomas are malignant, nonepithelial neoplasms derived from notochordal tissue.
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