448 MR. p. H. CABPENTEK ON THE GENDS ACTINOMETEA. 



admits) that it gives off no branches except the very small ones 

 which go to the tentacles. It is true that in the Ophiuridce the 

 radial ventrally-placed nerve does give off branches which go to 

 the muscles, besides those proceeding to the tentacles, as described 

 by Lange*, Teuscherf, and SimrothJ; but the researches of the 

 first-mentioned observer render it very doubtful whether the re- 

 presentative in the Ophiuridae of the subepithelial band of Gomatula 

 takes any part in the formation of these branches. 



That the subepithelial band is of the same nature in the Crinoida 

 and Asterids there can, it seems, be little doubt ; and it is there- 

 fore somewhat interesting that its nervous nature in the As- 

 terids has recently been disputed by Lange §, who regards 

 as nervous only two cellular masses separated from the subepi- 

 thelial fibrillar band by a connective-tissue membrane, and pro- 

 jecting into the lumen of the nerve-canal, which swell under the 

 pigment-spot into a large ganglionic mass ; while the subepithe- 

 lial band, together with the ciliated epithelium and the cuticula, 

 constitutes a protecting integumentary layer. 



Lange finds a corresponding condition in OpJiiura texturata, in 

 which the radial nervous system is better developed than in the 

 Asterids, and consists of a series of paired ganglionic masses 

 connected with one another by transverse and longitudinal 

 commissures. On the ventral side of this ganglionated cord is 

 a longitudinal band, which Lange regards as the homologue of 

 the protecting integumentary layer forming the floor of the 

 arabulacral groove of the Asterids, and which, as universally ad- 

 mitted, corresponds to the subepithelial band, epithelium, and 

 cuticula of the ambulacral grooves of the Crinoids. 



Lange's views have been partially accepted by Simroth ||; but 

 they have been altogether denied by Teuscher% who regards 

 Lange's nervous cell-masses in the Asterids simply as an epithe- 

 lial layer several cells deep on the inner wail of the nerve-canal, 

 while the terminal ganglionic mass under the eye-spot is repre- 

 sented by Teuscher as a cushion of connective tissue. 



* "Beitrage zur Anatomie und Histiologie der Asterien und Ophiuren," 

 Morphologisches Jahrbuch, Band ii. 1876, p. 241. 



t " Beitrage zur Anatomie der Echinodermen. — II. Ophiuridse," Jenaiscbe 

 Zeitsoln^ift, Bandx. 1876, p. 274. 



I "Anatomie und Schizogonie der Ophiactis vireiis, Sars," Theil I., Zeitsclirift 

 fur wissenschaftliche Zoologie, Band xxvii. p. 473. 



§ Log. cit. p. 274. || Loc. cit. pp. .556, 560. 



% 'Beitrage,' &c. III. "Asteriden,'' Jen. Zeitschr. x. p. 513. 



