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Brief Description: Helix is a genus of common snails. It belongs to family Helicidae. The most well known species are: Helix aspersa and Helix pomatia. External features (Helix aspersa): In addition to the hard calcareous shell that covers and protects the internal organs, the head and foot region can be observed when the snails are fully extended. When they are active, the organs such as the lung, heart, kidney and intestines remain inside the shell; only the head and foot emerge. The head of the snail has two pairs of tentacles: the upper and larger pair contains the eyes, and the lower pair is used to feel the ground. The mouth is located just underneath the head. The tentacles can be withdrawn or extended depending on the situation. The mouth has a unique tongue called a "radula" that is composed of many fine chitinous teeth. This serves for rasping and cutting food. From April and throughout the summer, the number of snails increases due to the high temperature and humidity which enhances the possibility of oviposition. The Pulmonate snails are hermaphroditic, meaning that both female and male sexual organs are present in the same individual. The snails produce both eggs and sperm in the ovotetis (also called the hermaphrodite gland), but it is later separated into two divisions, a sperm duct and oviduct, respectively. Mating takes several hours, sometimes a day. A few days after mating, the eggs are laid in the soil. They are usually 4-6 mm in diameter. The young snails mature through one or more years. This depends on where the snail lives. For example, maturity takes two years in Southern California, while it takes only ten months in South Africa. The size of the adult snails slightly varies with species. The life span of snails is on average two or three years. Some snails may live longer, perhaps even 30 years. Many deaths are due to predators and parasites. 
Bibliography: Feldkamp, Susan (2002). Modern Biology. United States: Holt, Rinehart, and Winston. pp. 725 Brusca & Brusca (1990). Invertebrates. Sunderland, Mass.: Sinauer Associates. Feldkamp, Susan (2002). Modern Biology. United States: Holt, Rinehart, and Winston. pp. 725 Brusca & Brusca (1990). Invertebrates. Sunderland, Mass.: Sinauer Associates.