250 THE VOYAGE OF H.M.S. CHALLENGER. 



He found all the sutural lines in tlie calyx of both species, including those between the 

 basals, to be " always plainly visible with a lens of moderate power ; " and he was there- 

 fore naturally surprised at the description of the calyx which was given by Sars as the 

 result of his study of the Norwegian specimens without interbasal sutures. In order to 

 verify the truth of his analysis of the calyx, Pourtales " forced a needle through the 

 central hole of the calice of a Rhizocrinus lofotensis until it split. The fractures followed 

 the joints between contiguous basals and between the latter and the first radials." 



These important observations were entirely overlooked by Ludwig,^ who followed Sars 

 in describing the subradial part of the calyx as an enlarged uppermost stem-joint. He took, 

 however, another and more correct view of the circular plate which Sars had called the 

 basal rosette (PI. VHIa. figs. 6, 7 ; PI. X. figs. 1, 4 — br) ; for he regarded it as an unusual 

 development of the calcareous network which occupies the central portion of the radial 

 funnel in all Crinoids (compare PL XX. figs. 4, 6, 8) and surrounds the plexiform gland 

 ascending from the chambered organ (PI. XXIV. figs. 8, 9 ; PL LVIII. figs. 2, 3 — rp). 



I have long ago expressed my acceptance'^ of this modification of Sars's views which we 

 owe to Ludwig ; but I could never quite reconcile myself to believe in the account which 

 he gives of the basals of Rhizocrinus. Having disestablished the rosette of Sars, he found 

 it necessary to seek elsewhere for the missing basals of this type ; and here he fell into 

 error, probably, I think, from a too exclusive reliance on his interpretation of sections 

 through the decalcified calyx, without properly considering the characters of an isolated 

 calyx minus its muscles and ligaments, such as was excellently figured by Sars in his 

 Tab. ii. fig. 43. 



A horizontal section through the upper part of the calyx (PL VHIa. fig. 7), or a view^ 

 of the calyx from above (PL X. figs. 1, 4), like those given by Sars, shows five (or six) 

 apparently interradial pieces (mp) surrounding the so-called basal rosette (br), and 

 occupying the interval between it and the large muscular and ligament-fossae on the 

 sloping distal faces. Sars considered these pieces, and rightly so, as integral parts of the 

 fii-st radials. Ludwig's sections, however, led him to believe that these pieces 

 (PL Villa, fig. 7, mp) " nieht radiiir, wie es nach der Sars' schen Autfassung sein miisste, 

 sondern interradiar liegen, so niimlich, dass stets die Mittellinie eines jeden Stiickes B in 

 die Trennungsebene zweier aueinanderstossender Radialieu fallt." ^ The interradial position 

 of the pieces in question is, however, shown just as well in Sars's figures as in those of 

 Ludwig, who had no real grounds for stating that Sars had indicated their boundaries 

 incorrectly. He considered that their interradial position precluded their being connected 

 with the radials, and was therefore led to regard them as " nach innen verschobene und 



-^o 



1 Zeitschr. f. wiss. ZooL. 1877, Bd. xxix. pp. 66-68. 



2 On some points in the Anatomy of Pentacrinus and Rhizocrinus, Journ. Anat. and Physiol, 1877, vol. xii. p. 50. 

 ^ The apparently interradial position of these pieces (mp) is more marked in Ludwig's figures, where they are lettered 



B, owing to the semidiagrammatic character of these figures and the omission of the interarticular and dorsal ligaments. 



