A LAND SNAIL 117 
The pericardial canal is opposite the ventricle and cannot be 
seen easily. The ureter may be easily traced. It is a wide 
canal which leaves the kidney at its forward end near the place 
where the pulmonary vein approaches the kidney; it first runs 
along the inner side of the kidney to its hinder end; here it 
doubles on itself and passes forward to the inner edge of the 
mantle, where it runs beside the rectum to a point near the 
respiratory pore dnd opens into the mantle cavity. 
It will be noticed that the heart and the kidneys are 
both asymmetrical organs. The heart has but one auricle; it 
will be remembered that in the pelecypod the auricles 
are paired organs ; one of the pair must thus be wanting in 
the snail. There is also only one kidney and one ureter, 
instead of a pair of each, as in the pelecypod. It is the left 
member of the pair in each case which is wanting. 
Exercise 4. Draw a view of the inner surface of the mantle on a 
scale of 38, showing the organs mentioned above; label all. 
The digestive system. Pass a bristle through the anus into the 
rectum in order to mark it. With two strong pins firmly fasten 
the extreme forward end of the animal’s foot and also its hinder 
end to the wax of the dissecting pan. With sharp, fine scissors 
cut through the floor of the mantle cavity and the collar in the 
median line ; carry the incision forward in the median line along 
the head between the base of the tentacles to the mouth. Care 
should be taken in making this incision not to cut the organs 
beneath. Spread the flaps as widely as possible to the right 
and left and pin them down, exposing thus the organs in the 
forward part of the body. 
The white organs on the right side of the body belong to the 
reproductive system. The large dark organ in the center, or 
on the animal’s left, is the stomach. Find the slender curved 
esophagus which leads forward from it to the dorsal side of the 
large muscular pharynx. The cesophagus is encircled by the 
