518 A. MILNES MARSHALL. 



than in A. rosace us. He considers that the subepithelial 

 band is alone to be regarded as the nerve, and points out that 

 the close histological similarity between this band in Crinoids 

 and the radial nerve of an Asterid, which latter, from the posi- 

 tion of the eyes, must certainly be nervous, is a strong argu- 

 ment in support of his view. He also discusses the claim of 

 the axial cords to rank as parts of the nervous system ; but 

 while admitting the great importance of Dr. Carpenter's ex- 

 periments, considers that the case is not yet satisfactorily 

 proved, and that the morphological diflBculties involved in the 

 possession by Crinoids of a nervous system altogether un- 

 known in other Echinoderms, are too great to permit the 

 acceptance of Dr. Carpenter's views. According to Ludwig, 

 the axial cords are parts of the connective-tissue basis of the 

 skeleton, which persist in an uncalcified condition, and are 

 probably nutritive in function. 



P. H. Carpenter, in a further paper on the arms of Cri- 

 noids,^ and in a monograph on the genus Actinometra,^ brings 

 forward strong additional evidence in support of the nervous 

 nature of the axial cords. He shows that in Antedon ro- 

 saceus the oral pinnules diflFer from the other pinnules, not 

 only in being destitute of tentacles (as pointed out by Dr. 

 Carpenter in 1865), but also in having no ambulacral groove, 

 no thickened ambulacral epithelium, and no trace of the 

 subepithelial band, i.e. that they are totally devoid of what 

 Ludwig considers to be the sole nervous system of Antedon ; 

 and yet these oral pinnules are peculiarly irritable, a slight 

 touch being sufficient to cause all ten arms to be suddenly 

 coiled up over the disc. 



He further finds that in Antedon Eschrichtii this ab- 

 sence of ambulacral groove and epithelium, and of the subepi- 

 thelial band, occurs not only in the oral pinnules, but at the 

 distal extremities of the arms and other pinnules. The allied 



' P. H. Carpenter, " Remarks on the Anatomy of the Arms of the Crinoids," 

 part ii, 'Journal of Anatomy and Physiology,' vol. xi, October, 1876. 



2 P. H. Carpenter, " On the Genus Actinometra," ' Transactions of the 

 Linnean Society,' 2nd series Zoology, vol. ii, part i, 1879. 



