NOTES ON EOHINODERM MORPnOLOaY. 615 



developed in the arms of the latter, bipolar cells being inter- 

 calated in their course. 



I have also seen these bipolar cells in Ant. Eschrichti, 

 Avliich type has further yielded me another important piece of 

 evidence. The existence of a fibrillar plexus, derived from the 

 axial cord, within tlie connective tissue forming the perisome 

 at the sides of the brachial ambulacra has long been known to 

 me. But until about a year ago I searched in vain for any 

 similar structure on the disc. At last, however, I succeeded 

 in following this plexus from the arm-bases down on to the 

 disc. It is extensively developed among the sacculi at the sides 

 of the ambulacra, and forms an annular network in the con- 

 nective tissue occupying the lip, but of course much further 

 from the mouth than the subepithelial ring discovered by 

 Ludwig. I detected this plexus first in a specimen which had 

 been stained with borax-carmine, and subsequently found it 

 also, though less readily visible, in haematoxylin preparations. 

 Last of all, on looking over the remains of my earliest sections, 

 made in Professor Semper's laboratory at Wiirzburg in the 

 winter of 1875-76, and stained with Beale's carmine, I was 

 able to make out traces of the same parambulacral network 

 which had originally escaped my notice.^ I have likewise 

 found it in the disc of A. antarctica, and even of A. rosa- 

 cea; and I have no doubt that the action of gold-chloride or 

 osmic acid on fresh material would bring it out in a more strik- 

 ing manner. 



I am strongly inclined to believe that extensions of this 

 plexus are in direct connection with the fibrils of the subepi- 

 thelial band, which is regarded by Ludwig as the sole nervous 

 apparatus in the Crinoid organisation. In fact, some histolo- 

 gists who have seen my preparations have expressed themselves 

 as having no doubt that this is the case. I hope, however, to 

 obtain some still better sections than those upon which this 

 opinion was based before finally adopting it as my own. In 



'* Preparations illustrating this structure were exhibited at the meeting of 

 the Zoological Society on December 19th, 1882, and will be figured iu the 

 " Challenger " report. 



