ME, P. H. CARPENTER ON THE GENUS ACTINOMETRA. 37 



subepithelial baud of Comatula takes any part in the formation of these branches. 

 Ludwig further admits that he has been quite unable to find any sense-organs at the 

 ends of the arms or pinnules of Comatula like those which exist in the Asteridea, and, 

 in discussing the views of Greeff, expresses it as his opinion (p. 78) that " die subepi- 

 theliale Faserlage, welche durchsetzt wird von fadenformigen Verliingerungen des dariibcr 

 gelegenen Epithels allein den Nerven darstellt." There can, I think, be little doubt 

 that this subepithelial band is of the same nature in the Crinoids and Asterids ; and 

 it is therefore very interesting that the nervous nature of this structure in the Asterids 

 has recently been disputed by Lange \ who regards as nervous only some cellular 

 masses separated from the subepithelial band by a lamella of connective tissue, and 

 projecting into the lumen of the two nerve-canals. He believes these cell masses to swell 

 into a large ganglionic mass beneath the pigment-spot ; while, in his opiniou, the sub- 

 epithelial band, together with the ciliated epithelium and the cuticula, constitutes a pro- 

 tecting integumentary layer. Lange finds a corresponding condition in Ophiura te.vlu- 

 rata, 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 longi- 

 tudinal band, which Lange regards as the homologue of the protecting integumentary 

 layer formiug the floor of the ambulacral groove of the Asterids, and which, as is uni- 

 versally admitted, corresponds to the subepithelial band, epithelium, and cuticula of the 

 ambulacral grooves of the Crinoids. 



Langc's views have been partially accepted by Simroth 2 ; but the correctness of them 

 is altogether denied by Teuscher 3 , who regards Lange's nervous cell-masses in the 

 Asterids simply as the " geschichtetes Epithel " on the wall of the nerve-canals; while 

 the terminal ganglionic mass under the eye-spot described by Lange is represented by 

 Teuscher (pi. xix. fig. 22) simply as a " bindegewebiges Polster." Ludwig 1 , too, speaks 

 of the nervous cell masses as local thickenings of the epithelium of the nerve-canals, which 

 are not present in every species. This is naturally a very strong argument against 

 Lange's views ; but Ludwig omits to apply similar reasoning to his own opinions regarding 

 the Crinoid nerves. The subepithelial bands {his nerves) are not constant in every 

 arm of many species of Actimomeira. Still less do Teuscher and Lange agree about the 

 nervous system of the Ophiurids ; Lange's ganglionic masses are described as artificial by 

 Teuscher, who, as in the Asterids, regards as the nerve only the fibrillar structure repre- 

 senting the subepithelial band of Comatula. 



The question is still an open one ; and it is therefore of no slight interest to learn that 

 the supposed ambulacral nerve, or subepithelial fibrillar band, is not always present in 

 the arms of Comatula, and that even when it exists it is certainly not motor in function, 

 even if it be a nerve at all 5 -, 



1 Morph. Jalirb. ii. 274. - Zeitseh. f. wiss. Zool. xxvii. pp. 550-500. 



3 " Beitr. &c, III. Astcriden," Jen. eitsch. x. p. 513. 



* "Beitrage zur Anatoinie der Aetoriden," Zeitschr. fur wiss. Zool. xxx. p. 191. 



s It is worth noticing here that the " ambulacral nerve " of Comatula must bo derived either from the niesoblast 

 or from the hypoblast of the embryo. It is developed immediately beneath the tentacular atrium of the pentacrinoid 

 larva, which Gotte has shown to be the most anterior portion of the left peritoneal sac. This is lined by hypoblast, 



