Medial ( Schulze, 1893 ) : Toward the median plane (Henle, 1855) of the body, in the frontal plane (Henle, 1855); the opposite of lateral (Barclay, 1803); used thus by Schulze (1893, p. 6). Also see Brusca & Brusca (1990, p. 46).

Oral-aboral axis ( Schulze, 1893 ) : Synonym for rostrocaudal axis; often preferred in the comparative anatomy of invertebrates; p. 5. Also see Willmer (1990, p. 15).

Rostral ( Schulze, 1893 ) : Toward the mouth along the longitudinal axis (Barclay, 1803) of the body; the opposite of caudal (Cleland, 1879); p. 6. Originally, toward the beak of a ship's prow ("rostrum"). In the BNA, His (1895) wrote, "The introduction of the word Rostrum for the cephalic pole of the axis of the body I deem an essential enrichment of our language. The adjective Rostral seems to me indispensable as an ontogentic expression." (p. 110; see translation by Eycleshymer, 1917, p. 109). Also see rostrocaudal axis.

Ventral ( Schulze, 1893 ) : Toward the belly of the body, or away from the back, in the transverse plane (Henle, 1855); the opposite of dorsal (Barclay, 1803). See Schulze (1893, p. 5), and Brusca & Brusca (1990, p. 46).