10 Ech. 
ECHINODERMATA. 
origin for the purpose of encircling the feet ; the succeeding rings are 
connected by one dorsal and two lateral vessels, which open freely and 
centrally in the body cavity ; the lateral vessels also send branches into 
the lateral arm -plates and arm- spines. The chief, or ventral, neural 
vessels communicate with the internal and more deeply situated vascular 
ring, which also encloses the central portion of the nerve-system. The 
trunks of this system give off branches in pairs to the “ vertebras ” and 
feet. A string on the internal (superior) face of the nervous band, 
Teuscher is inclined to regard (with Lange) as a vessel corresponding 
to the central vessels of the longitudinal septum in Asteridce ; in 
other respects, Lange’s partial exposition of the nervous system of 
Ophiuridce is hardly reconcilable with that of Teuscher, because of the 
discrepancy of the histological results of their investigations. What 
Teuscher describes as the nervous band, is, according to Lange, for a 
great portion, an epithelial band, homologous with that of the starfishes, 
but covered up by the closing of the ambulacral furrow through the 
ventral dermal plates. To Semroth (17) we are indebted for the first 
anatomical account of the anatomy of an Ophiurid (Ophiactis virens), 
comprising all parts of its organization. An abstract, however, is hardly 
possible here. 
Anatomy of Crinoids. It is evident from the different and indepen- 
dent investigations of the anatomy of recent Crinoids (3, 4, 7, 12, 13, 
20), that there exists in their arms and “ pinnulae,” above the skeleton 
and the muscles, two large canals, which are diverticula from the body- 
cavity ; an inferior or dorsal (canalis cosliacus, Teuscher’s “ Muskel- 
gefass ”), and a superior or ventral, often bipartite (canalis suhtentacu- 
laris, Teuscher’s “ Seitengefiisse,” described erroneously by J. Mul- 
ler as the “ tentacular” cavity). Between these two canals, lies a third, 
much narrower, communicating with the two other canals through 
delicate “ canaliculi,” or vessels, according to Teuscher (20) ; it encloses 
the genital string, in which (especially in its dilated portion in the 
lower pinnulse) the ova and sperma are developed ; it was described 
by J. Muller erroneously as the nerve. (In some species [Actinometra 
armatd] the production of eggs is not limited to the pinnulae, but takes 
place also in the true arms.) Above the “ subtentacular ” cavity are 
placed, from above downwards, (1) in the very bottom of the ambu- 
lacral furrow the (sometimes divided, or double) nerve-band, giving off 
branches to the tentacles (feet) ; (2) the nervous vessel ; (3) a muscular 
band; (4) the true ambulacral vessel, or water-tube, giving off the 
ordinary lateral branches for the tentacles. The nerve-vessels and the 
nerve-trunk are continued to the mouth, which is surrounded by their 
annular central parts, the three rings lying in the same order as in the 
arms. Numerous delicate tubuli, comparable tothe“Polian vesicles,” 
or “ stone-canals ” of other Echinoderms, hang down, ending open (?) in 
the body-cavity, from the aquiferous vascular ring ; numerous coecal 
prolongations also spring from the nervous vascular ring (12). In 
Rhizocrinus, only five (in 5-rayed specimens) “ stone canals ” are present, 
and the same number holds good for tlie tubular perforations of the 
perisoma, which in other Crinoids occupy, in large number, its superior 
