The garden snail: respiration and excretion.

What goes in must come out.

It may seem bizarre to link breathing with excretion but Cornu aspersum has no such qualms. Its pneumostome (blowhole) and anus are positioned next to each other on the right of its body, just under the lip of its shell. Evolution and the necessity to pack all its organs inside its carapace have produced this unlikely arrangement. The snail has neither diaphragm nor ribs and uses the floor of its single lung cavity to draw air in and out. This cavity is rich in hemolymph, which corresponds to both human blood and lymph. It lacks haemoglobin and is therefore a blue/grey colour, flowing freely inside the body rather than through veins and arteries. Cornu aspersum uses copper not iron to bind oxygen. It usually breathes infrequently, perhaps every minute or so, and its blowhole opens and shuts as it does so.

That is a snail modesty refusing to show its apertures to the general public and, like Henry V, turning its best side to be portrayed. 

By contrast to its breathing, Cornu aspersum excretes often. (Mine poop all the time, all over the place and in different colours. They particularly favour upside down on the roof). The excretory system centres around a kidney which filters nitrogenous waste products from the hemolymph and expels them. In the wild this returns vital nutrients to the soil. By eating and processing decaying vegetation and fungi which would otherwise rot and accumulate, it is a great asset to your garden's ecosystem and could be forgiven for chomping on your delicious letuces.