REPORT ON THE CRINOIDEA. 123 
himself to have traced the connection of the ultimate fibrils with those in the tactile 
papillee of the tentacles.! ; 
The discovery of this extensive perisomic or parambulacral network, derived from the 
axial cords of the arms and pinnules in various species both of Antedon and of 
Actinometra, led me to suspect its presence at the sides of the disk-ambulacra ; and 
after several unsuccessful attempts, chiefly due to the poor state of preservation of my 
material, I met with one disk of Antedon eschrichti which yielded the most satisfactory 
results. Portions of two sections are shown in Pl. LIX, figs. 6 and 7; while woodeut 
fig. 8 embodies the result of my studies of a few successive sections in the same series. 
g.V. 
Fig. 8.—Diagrammatic transverse section of an ambulacrum on the disk of Antedon eschrichti, x 70. 
a.d., The parambulacral nervous network—this is filled in from a few successive sections, only isolated portions of it being 
visible in any single one; a.e., ambulacral epithelium ; 0, radial blood-vessel; g.v., genital vessel; , radial or 
ambulacral nerve, the subepithelial band 3 8a., saceuli; Séc, subtentacular canal; ¢.b., tentacular branch of w, the 
radial water-vessel ; w.p., water-pores, 
There appears to be a good deal of individual variation ; but in this one species, at 
any rate, the elevated folds of perisome which bear the ambulacra contain a wonderfully 
rich network of delicate fibrils of precisely the same nature as those which occur at the 
sides of the brachial ambulacra (PI. LX. fig. 6, a’); and the brachial plexus may be 
followed down on to the disk at the sides of the food-groove (woodeut, fig. 8, a.d.). 
I have very little doubt that it is joined by branches which proceed upwards into the 
ventral perisome from the axial cords within the radials and lower brachials. But as 
' Comptes rendus, t. xevii. p. 188. 
