REPORT ON THE CRINOIDEA. 113 
Crinoids, one is not surprised to find Ludwig limiting himself to the following statement— 
“Die winzigen Zellen, die sich zwischen den Nervenfasern finden, sind vielleicht auch nur 
die Kerne von Zellen, die in den Verlauf der Fasern eingeschaltet sind ;”* and my own 
observations have not enabled me to add anything to this suggestion. 
Hamann’s observations on the Asterids have led him to discover that the so-called 
ambulacral nerves are only specially developed parts of a general subepithelial plexus 
containing ganglion-cells. This surrounds the whole body, and is traversed, though very 
sparingly, by vertical fibres extending downwards from some of the “Stutzzellen”; while 
sense-cells are intercalated among these at the bases of the respiratory ceeca and elsewhere. 
Hamann has found a similar ectodermic plexus, distinct from the radial nerve, in 
Holothurians; and the presence of a corresponding structure in Coelenterates, Nemertines, 
Turbellarians, Cheetognatha, &c., is now thoroughly established. Thus, then, there 
would seem to be no reasonable doubt respecting the existence of an ectodermic nerve- 
plexus in the Crinoids. But even if the existence of this plexus be admitted, it is 
difficult to suppose that the nervous system of a Crinoid with its innumerable pairs of 
muscular bundles is limited to the subepithelial band in the floor of the food-grooves, its 
tentacular branches, and the as yet undemonstrated 
plexus. Leaving the latter out of consideration for the 
moment, Where, I would ask, are the nerves of the pin- 
nules of Antedon acoela and Antedon angusticalyx 
which are shown in PI. LIV. figs. 1-3, 5% Where is the 
nervous system of the large number of arms on the two 
posterior rays of the gigantic Actinometra magnifica 
represented on Pl. LVI. fig. 7, or that of the numerous 
ungrooved arms on the three other rays 4 
It isdifficult toconceive that these ungrooved arms and 
pinnules (Pl. LXI. fig. 3), which form so large a part of 
the entire organisation of this animal, are entirely unpro- 
vided with a nervous system, and yet the ambulacral nerve 
Fic. 4.—Diagrammatic transverse section of 
is altogether absent (fig. 4). Even when this is present, Sere rece TAGE Te eoeb cera 
metra parvicirra, x 50. a, axial cord ; 
: : : a’, the branches proceeding from it; c.c., 
Ludwig himself admits that he has seen no other branches Gialiag’ eal’? dee, \elliataal” etip 5 Gk: 
2 5 c connective tissue spaces in the perisome ; 
proceeding from it than those which supply the tentacles. g.c., genital canal; g.v., genital vessel ; 
we 2 m j, skeleton of the pinnule-joint; Z.c., 
Now the muscular system of a Crinoid is unusually lateral canal connecting the coeliac and 
5 subtentacular canals; ov, ovary; s.¢.c., 
well developed. From the first radials to the ends of subtentacular canal; w., radial water- 
vessel. 
the arms every two joints are united by a pair of 
muscular bundles (Pl. LXI. figs. 4,5), except in the case of the syzygies and the rare liga- 
mentous articulations. The pinnules are always united to the arms by muscles, and in many 
forms there are muscles between several pairs of the pinnule-joints (fig. 6 on p. 121, m). 
1 Crinoideen, loc. cit., p. 264. 
(ZOOL. CHALL, EXP.—PART XXx1I.—1884.) Ti 15 
