The structure and compositon of the love dart (gypsobelum) in Helix pomatia.

The love dart of the snail Helix pomatia is a four-bladed, hollow spicule of calcium carbonate. The calcium carbonate is largely in the form of microcrystalline aragonite, the crystals being not more than 0.5 micrometer in size but assembled into sheets or blocks of much greater size. Protein occurs in the dart structure as an external sheath, as a lining to the tubular core and as a matrix component of the mineral phase. Comparisons with the molluscan shell are drawn and a rationale for the architecture suggested.