Educational Programs Available on Marco Island 🌴 Making the Shell begins before the snail is fully grown while it's still developing in its tiny larval stage .Shell glands secrete proteins at the base of the shell then the calcium carbonate is secreated on this base. The shell spirals as it grows. A protein layer is secreated over the minerals for coloration and to protect the shell. Process begins with the shell gland a small invagination from which the ingredients to make the shell are secrea