Oxford Academic is home to a wide variety of products. View the institutional accounts that are providing access.
View your signed in personal account and access account management features.Some societies use Oxford Academic personal accounts to provide access to their members.Ĭlick the account icon in the top right to: See below.Ī personal account can be used to get email alerts, save searches, purchase content, and activate subscriptions. Some societies use Oxford Academic personal accounts to provide access to their members. If you do not have a society account or have forgotten your username or password, please contact your society.
Do not use an Oxford Academic personal account.
Society member access to a journal is achieved in one of the following ways: If you cannot sign in, please contact your librarian. If your institution is not listed or you cannot sign in to your institution’s website, please contact your librarian or administrator.Įnter your library card number to sign in. Following successful sign in, you will be returned to Oxford Academic.When on the institution site, please use the credentials provided by your institution.Select your institution from the list provided, which will take you to your institution's website to sign in.Click Sign in through your institution.Shibboleth / Open Athens technology is used to provide single sign-on between your institution’s website and Oxford Academic. This authentication occurs automatically, and it is not possible to sign out of an IP authenticated account.Ĭhoose this option to get remote access when outside your institution. Typically, access is provided across an institutional network to a range of IP addresses. If you are a member of an institution with an active account, you may be able to access content in one of the following ways: Get help with access Institutional accessĪccess to content on Oxford Academic is often provided through institutional subscriptions and purchases. Identification of nonadaptive variation which results from developmental dependence on another character is dependent on the study of the selective and direct-environmental causes of variation in land snail shell form. A recurring problem in the explanation of shell form is the interpretation of covarying shell characters. Shell coiling sometimes occurs in the opposite direction between sympatric species, probably as a result of selection for reproductive isolation. Surprisingly, only a weak relationship exists between shell thickness and moisture conditions. Snails living on calcareous substrates sometimes have thicker shells the effect is not necessarily direct. For unknown reasons, helicid species in the Mediterranean area frequently have forms with keeled and with rounded shell peripheries. Relative shell height of snail species relates to the angle of the substrate on which activity occurs this could be related to the mechanics of shell balance. Apertural denticles are generally thought to represent adaptations to reduce predation. This pattern is variously interpreted as relating to the maintenance of constant attachment area/weight, whether of foot surface area when the snail is active or when attached to a substrate or of aperture perimeter when attached. Larger snails tend to have higher whorl expansion rates. Relative aperture area tends to be smaller under drier conditions, probably because of selection for smaller whorl cross-sectional area to reduce water loss. Snails may attain smaller adult sizes at higher population densities, apparently through the effects of pheromones on growth rate. Larger snails are often associated with moister conditions the effect may be inductive (direct) or selective, but the mechanism is not documented. Size variation generally has a large genetic component. For no character are there general rules relating shell form to environmental characteristics, although certain correlations are common. Variation in land-snail shell form has been extensively documented, but its causes are poorly understood.