n apertures, between the oral cavity and the pharynx
(ph.). "Pharyux" is here used in a wider sense than in the true
vertebrata; it reaches back close to the liver, and is therefore
equivalent to pharynx + oesophagus + a portion or all of the stomach.
The [so-called] hyoidean apertures are not equivalent to the
similarly-named parts of the vertebrata. Behind the pharynx the
intestine (int.) runs straight out to the anus (an.), which opens not in
the middle line, as one might expect, but in the left side! The liver lies
usually on the creature's right, and instead of being a compact gland,
is simply bag-like.

Section 5. The circulation is peculiarly reduced (Figure 2). The
cardiac aorta (c.ao.) lies along the ventral side of the pharynx, and
sends branches up along the complete bars between the gill slits.
There is no -distinct- heart, but the whole of the cardiac aorta is
contractile, and at the bases of the aortic arches that run up the bars
there are contractile dilatations that assist in the propulsion of the
blood. Dorsal to the pharynx, as in fishes, there is a pair of dorsal
aorta (d.ao.) that unite above the liver (compare the frog, for instance),
and thence run backward as a median dorsal aorta (d.ao.'). A portal
vein (p.v.) bring blood back from the intestine (and apparently from the
whole posterior portion of the animal) to the liver. Thence hepatic veins
(hep.) take it to the cardiac aorta.

{Lines from First Edition only.}
-When we remember that in the embryonic vertebrate the heart is at
first a straight tube, this circulation appears even more strikingly
vertebrate in its character than before.-

Section 6. The coelom, or body cavity, of Amphioxus lies, of course,
as in the vertebrata, between the intestinal wall and the body walls,
and, just as in the vertebrata, it is largely reduced where gill slits
occur. But matters are rather complicated by the presence of an
atrial cavity round the pharynx, which is not certainly represented in
the vertebrata, and which the student is at first apt to call the body
cavity, although it is entirely distinct and different from that space. The
mutual relation of the two will become apparent after a study of
Figures 10, 11, 12 (Sheet 21). Figure 10 gives diagrammatically a
section of a very young stage of Amphioxus; P is the pharynx portion
of the alimentary canal, coe. is the coelom surrounding it at this stage
here as elsewhere; mt.c. are certain lym