REPORT ON THE CRINOIDEA. 



123 



liimself to have traced the connection of the ultimate fi1)rils with those in tlie tactile 

 paj^ilJae of the tentacles.' 



The discovery of this extensive perisomic or paramhulacral network, derived from the 

 axial cords of the arras and pinnules in various species both of Antedon and of 

 Actinometra, \iii\ nie to suspect its presence at the sides of the disk-amljulacra ; 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 j'ielded the most satisfactory 

 results. Portions of two sections are shown in PI. LIX. figs. G and 7 ; while woodcut 

 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 ambnlacruni on the disk of Antedon eschrichti, x 70. 

 a.d., The parambulacral nervous networli — this is filled in from a few successive sections, only isohated portious of it being 

 visible in any single one; a.c, ambulacral epithelium; b, radial blood-vessel; g.v., genital vessel; n, radial or 

 ambulacral nerve, the subepithelial baud; sa., sacculi ; Stc, subtentacular canal; t.b., tentacular branch of w, the 

 radial water-vessel ; u'./'., water-pores. 



There appears to be a good deal of individual variation ; l)ut 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 amliulacra (PI. LX. fig. 6, a,') ; and the brachial plexus may be 

 followed down on to the disk at the sides of the food-groove (woodcut, 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 ])rachials. But as 



1 Comptes rendus, t. xcvii. p. 188. 



