Definition: An interaction relationship between two organisms living together in more or less intimate association in a relationship in which both organisms benefit from each other
Definition: a comparatively thin, typically horizontal layer within a fluid, in which a property of the fluid varies greatly over a relatively short vertical distance
Definition: The institution that holds a type specimen for a given species. The recommended best practice is to use the identifier in a collections registry such as the Biodiversity Collections Index (http://www.biodiversitycollectionsindex.org/).
Definition: Eye-spots which may be set into a pit to reduce the angles of light that enters, to allow the organism to deduce the angle of incoming light. Lens-like structures may be present, but stemmata, unlike lens eyes, cannot form an image, either for lack of refractive power or retinal resolution.
