414 THE VOYAGE OF H.M.S. CHALLENGER. 
Lovén has recently pointed out the singularly Crinoidal appearance of the calycinal 
system of a Triassic Urchin, Tiarechinus princeps, Laube.! “The relative magnitude of 
the entire system, the prominent share it takes among the constituents of the skeleton, 
the forms and proportions of its parts, are such as forcibly to recall the calyx of some 
Palxocrinoid, and to justify a desire to turn the Echinoid upside down and to see the 
Fic. 21.—Tiarechinus princeps, Laube, 
inverted so as to show the resemblance 
of its apical system to the calyx of a 
Crinoid. (The figure, but not the 
letters, after Lovén.) B, basal; 
7, single, median interradial ; 7, lateral 
interradials; R, radial. 
calycinal system in its imaginary original position, when it 
formed a part of some remote ancestral type. In this respect 
the resemblance becomes still more striking.” 
Let us compare Lovén’s figure (fig. 21) with that of the 
Blastoid (fig. 20). Each has relatively large basals (B) ; but 
the radials of the Pentremite (2) are small in Tiarechinus, 
their limbs being replaced by the two lateral plates of the 
interradius (7) which enclose the ambulacrum. In Tiare- 
chinus, just as in the Blastoid, however, the ambulacrum ends 
against the body of the corresponding radial ; and its nerve, 
lying beneath the ambulacral plates as in recent Echini, 
would be in a position where it could be directly continuous 
with an axial cord situated within the radial or on its inner 
face, if only Tiarechinus were a Crinoid instead of an Urchin. I would not, of course, 
be understood as saying that Tiarechinus had a central capsule and axial cords pro- 
ceeding from it. My only object has been to point out that Lovén’s happy comparison 
of this curious type with an inverted Crinoid affects other systems of organs besides that 
of the calycular plates. 
At the same time, considering the number of Asterids which 
have a calyx of relatively large plates, and the fact that there is a continuous nerve 
sheath on the dorsal surface, I think it not improbable that indications of a central 
capsule and axial cords may eventually be discovered in the Echinozoa. 
It remains now to notice the observations of Dr. Jickeli, which, though only published 
recently, are nearly four years old.” Like Marshall he has made an elaborate series of 
experiments in extension and confirmation of those originally described by Dr. Carpenter, 
whose views respecting the nervous nature of the central capsule and axial cords he 
adopts unreservedly. He further believes that the fibrillar bundles uniting the cirrus- 
joints and those forming the dorsal and interarticular ligaments (as they are described 
above) in the arms (Pl. LXIL., /d, 7’) are muscular in function, though differing in many 
points from the fibres. which have hitherto been exclusively described as muscles 
(Pl. LXII., m); for when the axial cord of a detached cirrus is stimulated “so kriimmt 
sich derselbe auf das Heftigste zusammen und geriith selbst in Tetanus. 
1 On Pourtalesia, loc. c2t., p. 65. 
3 
2 Vorliufige Mittheilungen iiber den Bau der Echinodermen, ], Ueber das Nervensystem und die Sinnesorgane 
der Comatula mediterranea, Zool. Anzeiger, vii. Jahrg., pp. 346-349 and 366-370, 1884. 
5 Zool. Anzeiger, vol. vii., 1884, p. 348. 
