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