Longitudinal plane ( Henle, 1855 ) : A plane of section passing through the longitudinal axis (Barclay, 1803) in animals with radial symmetry, dividing the body into roughly equal longitudinal halves; term alluded to by Henle (1855, p. 1). In animals with bilateral symmetry there are two orthogonal longitudinal planes, the sagittal plane (Henle, 1855) and frontal plane (Henle, 1855). A synonym is rostrocaudal plane.