![Picture](/uploads/3/1/6/2/31629889/365339_orig.png)
Like other pulmonate land gastropods, the majority of land slugs have two pairs of 'feelers' or tentacles on their head. The upper pair is light sensing and has eyespots at the ends, while the lower pair provides the sense of smell. Both pairs are retractable, and can be regrown if lost.[citation needed]
On top of the slug, behind the head, is the saddle-shaped mantle, and under this are the genital opening and anus. On one side (almost always the right hand side) of the mantle is a respiratory opening, which is easy to see when open, but difficult to see when closed. This opening is known as thepneumostome. Within the tissue of the mantle in some species is a very small, rather flat shell, or in some other cases a collection of calcareous granules.[citation needed]
Like most gastropods, a slug moves by rhythmic waves of muscular contractionon the underside of its foot. It simultaneously secretes a layer of mucus that it travels on, which helps prevent damage to the foot tissues.[3] Around the edge of the foot is the 'foot fringe' or 'skirt'.[citation needed]
Vestigial shellMost slugs retain a remnant of their shell, which is usually internalized. This organ generally serves as storage for calcium salts, often in conjunction with the digestive glands.[4] An internal shell is present in the Limacidae[5] and Parmacellidae.[6] Adult Philomycidae,[5] Onchidiidae[7] and Veronicellidae[8] lack shells.
On top of the slug, behind the head, is the saddle-shaped mantle, and under this are the genital opening and anus. On one side (almost always the right hand side) of the mantle is a respiratory opening, which is easy to see when open, but difficult to see when closed. This opening is known as thepneumostome. Within the tissue of the mantle in some species is a very small, rather flat shell, or in some other cases a collection of calcareous granules.[citation needed]
Like most gastropods, a slug moves by rhythmic waves of muscular contractionon the underside of its foot. It simultaneously secretes a layer of mucus that it travels on, which helps prevent damage to the foot tissues.[3] Around the edge of the foot is the 'foot fringe' or 'skirt'.[citation needed]
Vestigial shellMost slugs retain a remnant of their shell, which is usually internalized. This organ generally serves as storage for calcium salts, often in conjunction with the digestive glands.[4] An internal shell is present in the Limacidae[5] and Parmacellidae.[6] Adult Philomycidae,[5] Onchidiidae[7] and Veronicellidae[8] lack shells.