On the Geotropic Orientation of Helix

The snail Helix nemoralis in negatively geotropic creeping orients upward upon an inclined surface until the angle of the path of progression (theta) is related to the tilt of the surface (alpha) as (Delta sin theta) (Delta sin alpha) = - const.; theta is very nearly a rectilinear function of log sin alpha. The precision of orientation (P.E.(theta)) declines in proportion to increasing sin alpha, P.E.(theta)/(theta) in proportion to theta. These facts are comprehensible only in terms of the view that the limitation of orientation is controlled by the sensorial equivalence of impressed tensions in the anterior musculature.