eye-like light sensors, and the lower two are tactile and olfactory sense organs. The snail extends the tentacles by internal pressure of body fluids, and retracts all four tentacles into the head by invagination when threatened or otherwise retreating into its shell. The mouth is located beneath the tentacles, and contains a chitinous radula with which the snail scrapes and manipulates food particles. The shell of Cornu aspersum is almost always right-coiled, but exceptional left-coiled specimens are also known; see Jeremy (snail) for an example. Taxonomy The accepted name of the species was long considered to be Helix aspersa, a member of the genus Helix. However, in a number of publications since 1990, it has instead been placed in various genera previously considered as subgenera of Helix. One such genus is Cornu, which is appropriate if the species is considered as congeneric with the species previously known as Helix aperta. Then the name would be Cornu aspersum. Previously there was debate whether Cornu was a valid generic name (because it was first applied to teratological specimens), but a 2015 ruling has confirmed that it is so. Until this was established, Italian research teams and others used the generic name Cantareus instead. Other workers, including Ukrainian and Russian research teams, who regard H. aspersa and H. aperta as being in different genera, call the former Cryptomphalus aspersus. It also still remains an arguable position to retain Helix as the generic name. Many subspecific varieties have been described on the basis of shell characters (e.g.). The most prominent example nowadays is the subspecies Cornu aspersum maximum (Taylor, 1883), originally described as a large shelled form from Algeria (but perhaps including similar forms from elsewhere). In the recent scientific literature the name has been applied both to large Algerian snails and to a large form found in snail farms. Some Algerian forms are indeed genetically quite distant from the usual, most widespread form, but the large form in snail farms is different again. It is also problematic that there was a prior use of the name Helix aspersa maxima unassociated with Algeria. The subspecies maximum is formally considered by some authorities as a junior synonym of Cornu aspersum. Life cycle Like other Pulmonata, individuals are hermaphrodites, producing both male and female gametes. Reproduction is predominantly, and probably exclusively, by outcrossing. During a mating session of several hours, two snails exchange sperm reciprocally. Cornu