Sheet 16.

Figure 1. Circulation of the Dog-Fish.
Figure 2. Simplified and more typical fish circulation,
in which the posterior cardinals have not coalesced in the
median line. The Cuvierian veins = the vena cava superior
of the higher type; the posterior cardinal is represented by
the azygos vein in the Rabbit.
Compare [Sheet 24], Figure 7, and [Sheet 2], Figure 2.
Figure 3. Side view of the pericardium.
a.br., afferent branchial artery.
a.c.s., anterior cardinal sinus (= internal jugular vein).
au., atrium (auricle) (= the two auricles of higher forms).
b.a., bulbus arteriosus.
c.a., conus arterious.
cd. a., caudal artery.
cd.v., caudal vein.
c.s., Cuvierian sinus.
d.a., dorsal aorta.
E., eye.
e.br., efferent branchial arteries.
g.s., in position of gill slits.
h.br.a., hypobranchial artery.
H.S., hepatic sinus.
[i.j.s., inferior jugular sinus (= external jugular vein).]
K., kidney.
L.V., lateral vein.
[oe.s., ventral wall of oesophagus.]
P.C.C., pericardial cavity.
P.C.S., posterior cardinal sinus.
p.p.c., pericardio-peritoneal canal.
P.V., portal vein.
r.p.v., reno-portal vein.
s.c.v., subclavian vein.
Vn., ventricle.
-v.s.v., inferior (= external) jugular vein-.
Figure 4. Skeleton of pectoral limb, and girdle.--
g., the girdle (also in Figure 3).
m.p., meso-pterygium.
mt.p., meta-pterygium.
p.p., pro-pterygium.
sc., its dorsal portion.

Sheet 17.
-The Uro-genital Organs of the Dog-Fish_.

Figure 1. The Female, the oviduct of the left side cut away,
-and an egg case in the oviduct.-
Figure 2. The Male.
The rectum is removed in both cases, and the silvery peritoneum
dissected off from the kidneys.
Figure 3. A generalized diagram of the uro-genital organs.--
All references in text.
Ms., the mesonephros, is the epididymis in the male, and is reduced
in the female; Ms.d., its duct, is the vas deferens in the male, and
persists only as the urinary receptacle in the female.
Mt. and Mt.d., the metanephros and metanephric duct, become the
functional kidney and ureter in both sexes. G. is the gonad
(reproductive gland), and M.L. the animal's middle line (median
plane).
-Ps.-, [Pr.,] the pronephros, is never developed in the Dog-fish;
P.d., its supposed duct, is the oviduct of the female, and is
suppressed in the male.