ead, and, less obviously, they occur with diminishing importance
as the scale of the vertebrata is ascended.

Section 8. If we compare the nervous system of amphioxus with that
of any vertebrate, we find at once a number of striking differences. In
the first place, the skeletal covering of it, the cranium and the neural
arches of vertebrae, are represented only by a greatly simplified
connective tissue. In the next, a simple and slight anterior dilatation
alone represents the brain. A patch of black pigment anterior to this
(e.s.) may or may not be what its name implies an eye-spot. There is
a ciliated funnel, c.f. (Figure 1, Sheet 19), opening on the left side,
which has been assumed to be olfactory in its functions, and in the
mouth chamber a ciliated pit (c.p.), which may, or may not, be an
organ of taste. The ventral fissure of the spinal cord is absent. The
dorsal nerves are without ganglia, and do not come off in pairs, but
alternately, one to the left, then one to the right, one to the left, one
to the right, and so on. The ventral nerves are very short, more numerous
than the dorsal, and never unite with these latter to form mixed
nerves.

The student will observe that here, just as in the case of the ciliated
funnel and anus, the Amphioxus is not strictly symmetrical, but
twisted, as it were, and so departs from the general rule of at least
external bilateral symmetry obtaining among the vertebrates. It
habitually lies on one side in the mud of the sea bottom, and it is
probable that this external asymmetry is due to this habit, so that
too much classificatory importance must not be attached to it. The
soles and other related fish, for instance, are twisted and
asymmetrical, through a similar specific habit, to such an extent that
both eyes lie on one side of the animal.

Section 9. No kidney on the vertebrate pattern is found, but the
following structures have, among others, been suggested as renal
organs:--

(a) Certain canals, the brown tubes of Lankester (b.t.L., Figure 2,
Sheet 19), a pair of pigmented tubes opening into the atrium at the
hind end of the pharynx, lying forward along by the dorsal coelomic
canals, and having an internal opening also.

(b) Certain tubuli described by Weiss as situated in a series along
the upper corners of the atrial cavity, and communicating, after the
fashion, of the "nephridia" of the earthworm, with the coelom and with
the exterior (or,