Keber's organ


Pericardium


Digestive gland |


Anterior retractor me ge 4 : Kidney
1 igi Posterior retractor


Posterior
- adduetor

Anterior %,

adductor

Exhalent

siphon


t—. Inhalent
siphon


Protractor


Mouth
Mantle of right side


Labial palps Left outer gill


Foot
Left inner gill


Fig. 45.—The Fresh-water Mussel (Anodonta). Shell removed. Part of the mantle of the left side
has been taken away so as to expose the gills, foot, etc.
(f) The visceral mass forming the upper two-thirds of the large foot, a
laterally compressed, oblong mass. The lower third is the muscular
portion of the foot, or foot proper.
(g) The pericardium, lying along the dorsal surface, beneath the hinge-
ligament. Within it is the heart. which consists of two auricles and
a ventricle. The ventricle surrounds the rectum, which passes through
the pericardium.
(h) The paired kidney or “organ of Bojanus,”’ lying just beneath the peri-
cardium, with which it communicates through two crescentic reno-
pericardial openings (nephrostomes) at the anterior end. [In Mytilus
the kidneys lie on the floor of the pericardium on either side of the
heart. |

(t) Keber’s organ or the pericardial gland, a glandular. reddish-brown
mass, lying in the anterior region of the body just in front of the
pericardium. [In Mytilus this gland does not occur. |


136 FRESH-WATER MUSSEL—COMMON MARINE MUSSEL


(j) The digestive gland or liver, a large organ surrounding the stomach and
the anterior end of the intestine.
