516 A. MILNES MARSHALL. 



as the true nervous system of Antedon, and as the represen- 

 tative of the radial nerves of other Echinoderms. 



In April of the same year P. H. Carpenter ^ confirmed Lud- 

 wig's description of the subepithelial bands which he had 

 himself independently discovered, and agreed with him in 

 regarding tliem as nervous. He also showed that the cord x, 

 described by Semper^ was not identical as he had supposed with 

 Perrier's fibrous cord, and that neither of these structures cor- 

 responded to the subepithelial band, Semper's cord being 

 merely a pigmented cellular thickening between the ambulacral 

 and subtentacular canals, while Perrier's fibrous cord is a 

 muscular band in the ventral wall of the ambulacral canal. 

 P. H. Carpenter, however, difi^ered from Ludwig in regarding 

 not only the subepithelial bands, but the axial cords also as 

 nervous, and he was the first to distinctly maintain the 

 existence in Antedon of this double nervous system in spite of 

 the morphological difficulties involved in this view. He brought 

 forward as additional evidence in favour of the nervous character 

 of the axial cords the fact that in the arms of Actinometra the 

 cord enlarges in the centre of each ossicle and gives off branches 

 to both dorsal and ventral surfaces, some of the latter reaching 

 " the bases, or in some cases even the tips of the respiratory 

 leaves.'' He even suspected a connection between some of 

 these branches of the axial cord and the subepithelial bands ; 

 some, he says, ^' appear to enter into the plexus of tissue 

 forming the organic base of the skeleton, others seem to be- 

 come connected with epidermic structures." 



In a supplemental note^ Dr. Carpenter also confirms the 

 existence of the subepithelial baud, and considers that it is 

 " by no means improbable, looking alike to its position and to 

 its histological character, that this band is a nerve." On 

 account mainly of its position he suggests that it is " an afferent 

 rather than a motor nerve." He also brings forward the 

 following extremely, important additional experimental evidence 



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

 'Journal of Anatomy and Physiology,' April, 1S7G. 



- Carpenter, 'Proceedings of the Royal Society,' vol. xxiv, 1876, p. 651, 



