THE NERVOUS SYSTEM OP ANTEDON ROSACEUS. 269 



granular substance and with very small cells imbedded in the fibrillar 

 tissue. He appears to have been unacquainted with Dr. Carpenter's 

 work, and, in spite of the resemblances he points out so clearly, denies 

 absolutely the nervous nature of the axial cords without stating 

 definitely his reasons for so doing. 



Semper, in 1874, 1 published an independent refutation of Midler's 

 error as to the genital rachis, and suggests, concerning the nervous 

 system, in ignorance of Dr. Carpenter's statement quoted above, " It 

 might even be possible that the cord in the interior of the calcareous 

 skeleton (i.e. the axial cord) is a nervous cord ; and if so, then the 

 so-called heart situated in the calyx would certainly have to be looked 

 upon as a ganglion." Semper also suggests that a fibrous cord described 

 by Perrier 2 as lying above, i.e. on the ventral side of the tentacular 

 canal, may also belong to the nervous system. He confirms the 

 existence of this cord, and refers to it as x in a diagrammatic transverse 

 section of an arm. 



In an addendum to the translation of Semper's paper 3 and in a second 

 communication to the Royal Society on the structure, physiology, and 

 development of Antedon rosaceus,* Dr. Carpenter further develops the 

 theory that the axial cords " are really nerve-trunks, and that the 

 five-chambered organ in the centrodorsal basin is their centre." He 

 refers to the " quickness and consentaneousness " with which the 

 coiling and uncoiling of the arms are effected, and to the fact that 

 irritation of the oral pinnules causes the whole circlet of arms to close 

 together 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 conse- 

 quently no need of the insulation which they require where nerve-fibres 

 of very different 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 



1 Semper, "Kurze Anatomische Bemerkungen ueber Comatula," ' Arbeiten aus clem Zool- 

 Zoot. Institut in Wtirzburg,' Band i,.1874, p. 259. Translated in the 'Annals and Magazine 

 of Natural History,' 1875, p. 202. 



2 Perrier, ' Archives de Zoologie Experimentale,' tome ii, 1873, p. 55. 



3 Carpenter, 'Annals and Magazine of Natural History,' 1875, p. 206. 

 1 Carpenter, ' Proceed'ngs of the Royal Society,' 1876, p. 226. 



