Snails hatch from eggs and are born with a rudimentary shell.
The protoconch or embryonic shell has a different sculptural pattern to the rest of the shell. This is the part of the shell the snail has when it is born.
Xanthomelon sp. with juvenile snail crawling
This shell grows with the snail. As it grows, the number of whorls increase. In many groups such as camaenids and pupinids, the adult snail shell has a reflected or thickened lip after which no further growth occurs. As a general rule, adult growth is achieved at 4.5 to 5.5 whorls. Semi-slugs have fewer whorls.
However, other snails such as charopids [pinwheel snails] and helicarionids [glass-snails] display non determinate growth and have the ability to keep adding to the shell after becoming adult in a phase known as gerontic growth.
Ramogenia challengeri
Facts About Snails 
What do snails eat in the wild? Is it the same as domesticated snails?
HI Afton. Australian snails eat fungus. If you mean the snails in your garden, then they are introduced from overseas and they are vegetarians. They will eat your garden plants. If you keep snails as pets, then you need to feed them to match what they eat in the wild eg the common garden snail loves carrot but our native snails love mushrooms and scraping the flesh off cucumbers.
my African land snail have born snails with out their shells
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