interesting of all animals. Man is at the highest summit, the lancelet
at the lowest root, of the vertebrate stem.

It lives on the flat, sandy parts of the Mediterranean coast, partly
buried in the sand, and is apparently found in a number of seas.* (*
See the ample monograph by Arthur Willey, Amphioxus and the Ancestry
of the Vertebrates; Boston, 1894.) It has been found in the North Sea
(on the British and Scandinavian coasts and in Heligoland), and at
various places on the Mediterranean (for instance, at Nice, Naples,
and Messina). It is also found on the coast of Brazil and in the most
distant parts of the Pacific Ocean (the coast of Peru, Borneo, China,
Australia, etc.). Recently eight to ten species of the amphioxus have
been determined, distributed in two or three genera.

(FIGURE 2.210. The lancelet (Amphioxus lanceolatus), twice natural
size, left view. The long axis is vertical; the mouth-end is above,
the tail-end below; a mouth, surrounded by threads of beard; b anus, c
gill-opening (porus branchialis), d gill-crate, e stomach, f liver, g
small intestine, h branchial cavity, i chorda (axial rod), underneath
it the aorta; k aortic arches, l trunk of the branchial artery, m
swellings on its branches, n vena cava, o visceral vein.

FIGURE 2.211. Transverse section of the head of the Amphioxus. (From
Boveri.) Above the branchial gut (kd) is the chorda, above this the
neural tube (in which we can distinguish the inner grey and the outer
white matter); above again is the dorsal fin (fh). To the right and
left above (in the episoma) are the thick muscular plates (m); below
(in the hyposoma) the gonads (g). ao aorta (here double), c corium, ec
endostyl, f fascie, gl glomerulus of the kidneys, k branchial vessel,
ld partition between the coeloma (sc) and atrium (p), mt transverse