ANATOMY OF THE CUNNER. 435 
extends straight along the median ventral line. The liver 
(Li) forms an elongated light-brown mass resting upon the 
stomach. The elongated gall-bladder lies between the 
liver and stomach, somewhat imbedded in the substance of 
the former. There is no pancreas, though it is present in 
some fishes. ‘The spleen (Sp) lies between the stomach and 
intestine, in the mesentery; it is dark reddish-brown in 
color. 
The air-bladder (8) is a single large sac, placed in the dor- 
sal part of the body-cavity. Its glistening walls are com- 
posed mainly of tough fibrous tissue. The pneumatic duct, 
by which the bladder communicates with the esophagus in 
many fishes, is wanting in the perch as in nearly all other 
Teleosts. The air-bladder normally contains only gases. It 
conceals most of the kidneys, which extend the whole length 
of the body-cavity on either side of the middle line, as two 
long strips of a deep though dull red. They project beyond 
the air-bladder in front (7) and behind (A7’). Their an- 
terior ends are somewhat separated from one another by the 
intervening pharynx. The ureters open into a urinary 
bladder (01) behind the anus. 
The ovary is single and varies greatly in size according to 
the season. In the male the sexual glands are double. Each 
testis (7) is an elongated, whitish, lobulated organ, placed im- 
mediately below the swimming-bladder, and continues pos- 
teriorly with the spermiduct, which opens immediately be- 
hind the anus. 
The heart (#7?) lies in the triangular pericardial cavity ; 3 ib 
consists of two portions, the dark-colored venous chamber, 
or auricle, above, and the lighter-colored arterial chamber, or 
ventricle, below. The auricle receives from above two large 
veins, one from either side; these veins are called the ducti 
Cuvieri. Each Cuvierian duct, as can be seen in the figure, 
ascends beside the cesophagus, and there receives a large jug- 
ular vein. from in front, and a large cardinal vein from be- 
hind. Furthermore, a large vein, the sole representative of 
the vena cava of higher Vertebrates, passes from the liver, 
near its anterior end, through the pericardium, and empties 
into the Cuvierian ducts near their common auricular orifice. 
