NERVOUS SYSTEM OP ANTEDON ROSACEUS. 515 



as strong evidence of the presence of a definite nervous system, 

 and suggests that the histological simplicity of the axial cords 

 may " be related to the fact that as the muscles are all flexors the 

 nerves have only one function to perform, and that there is 

 consequently no need of the insulation which they require 

 where nerve-fibres of very diflFerent functions are bound up in 

 the same sheath." 



He further supports his theory by the following experiment 

 made at Oban in 1867, and which for convenience of reference 

 I shall describe as 



Experiment A. — The entire visceral mass was removed 

 from a living specimen so as to leave nothing but the calyx 

 with the central capsule and its prolongations and the arms. 

 A needle was then passed down the canal surrounded by the 

 First Radials (cf. fig. 1) so as to irritate the chambered organ. 

 "All the ten arms then suddenly and consentaneously closed up. 

 On the withdrawal of the needle the arms gradually straightened 

 themselves again, and again coiled up as before when the irrita- 

 tion of the central organ was renewed.'"' 



In January, 1876, Greef ^ called attention to the thickened 

 epithelium forming the floor of the ambulacral grooves both of 

 the arms and disc. He pointed out the close correspondence 

 both in position and histological structure between this ambu- 

 lacral epithelium of Antedon, and the radial nerves and circum- 

 oral commissure of a Starfish, and suggested that the former, 

 like the latter, was nervous in function. At the same time he 

 denied the nervous character of the axial cords. 



In the following mouth Ludwig,"- without being acquainted 

 with GreePs work, described for the first time a " delicate 

 fibrillar band " immediately beneath the ambulacral epithelium, 

 i. e. what we have named above the subepithelial band (fig. 2, A), 

 which he regarded on histological and morphological grounds 



' Greef, " Ueber den Bau der Criuoideeu," ' Sitzuugsb. d. Gesellsch. z. 

 Beford. der gesam. Naturwiss. zu Marburg,' No. 1, 1S76, pp. 16—29. 



- Ludwig, ' Nachrichteu v. der Kouigl., Gesellschaft der Wisseuschafteu, 

 und der Uuiversitat zu Gottingen,' No. 5, Feb. 23rd, 1876. 



