Alphabetical list

Radial nerve cord ( Galen, c173 ) : A topographic division that is a differentiated linear zone of the nerve net in Echinoderms with periodic small ganglia (Galen, c173) along its length, and extending into each of the (most commonly five) arms from the circumoral nerve ring. There is no convincing evidence that the Echinoderm nervous system (Monro, 1783) is divided into central nervous system (Meckel, 1817) and peripheral nervous system (Meckel, 1817); see Cobb (1995, p. 411). A cord segment between two adjacent ganglia is called a longitudinal communicating branch. more details

Radial symmetry : Symmetry around the longitudinal axis (Barclay, 1803) of the body; see Willmer (1990, p. 15), Brusca & Brusca (1990, p. 44). more details

Reference term : Synonym for standard term. It is not preferred because of possible confusion with literature references. more details

Region : Shortened form of gray matter region, though other definitions are found in the literature. more details

Rhombencephalon ( His, 1893b ) : Latin synonym for rhombicbrain (His, 1893b); p. 173. more details

Rhombicbrain ( RB ; His, 1893b ) : The caudal (Cleland, 1879) of the three primary brain vesicles-the primary hindbrain vesicle (Baer, 1837)-of the vertebrate neural tube (Baer, 1837) develops into the adult topographic division, the rhombicbrain. The latter contains the hindbrain (Baer, 1837) or synonymous secondary hindbrain (Sharpey et al., 1867)-which is the cerebellum (Aristotle) and pons (Haller, 1747)-combined with the medulla (Winslow, 1733) or afterbrain (Baer, 1837). His introduced rhombicbrain for macrodissected adult vertebrates (in the original German, "Rautenhirn", p. 173), and Herrick (1915, p. 121), for example, applied the English form used here. Synonyms include rhombencephalon (His, 1893b), epencephalon (Owen, 1868), hindbrain (Carpenter, 1976). more details

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. more details

Rostrocaudal axis : Equally acceptable synonym for longitudinal axis (Barclay, 1803), but also indicating polarity or direction toward the oral (Schulze, 1893) or rostral (Schulze, 1893) end, or toward the aboral (Schulze, 1893) or caudal (Cleland, 1879) end, of the axis; see oral-aboral axis (Schulze, 1893); used recently by for example Kuhlenbeck (1973, p. 111), Nauta & Feirtag (1986, pp. 39-40) and Swanson (2003, pp. 223-228). more details

Rostrocaudal plane : Synonym for longitudinal plane (Henle, 1855). more details

Route : The physical course taken by a connection through gray matter regions and/or white matter tracts. more details