f>8 Dr. W. B. Carpenter. [May 29, 



between the two principal canals (etc and cc) in the arms of Crinoidea, 

 which had been regarded by Professor J. Miiller as a nerve, really 

 belongs to the reproductive apparatus ; and further, that I had been led 

 to regard as a nerve-trunk the solid cord (ax) which traverses the axial 

 canal of each calcareous segment of the rays and arms, through 

 finding that this cord gives off a regular system of branching fibres 

 (nm, nm) to the muscular bundles (TO, m) which intervene between the 

 calcareous segments, and which flex the arms by their contraction. 



In a further communication on this subject made to the Royal 

 Society at the beginning of 1876, I supported this view by experi- 

 mental evidence;* showing that in an eviscerated specimen of Antedon, 

 irritation of the qninquelocular organ (contained in the centre-dorsal 

 basin) from the walls of which the radial cords proceed, produces a 

 sudden and simultaneous contraction of the flexor muscles of the 

 arms, similar to that which I had mentioned in my Memoir ( 13) as 

 resulting in the natural condition of the animal from irritation of its 

 oral pinnules. 



That the supposed nerve of Miiller is really what I stated it to be 

 a genital rachis had been independently ascertained by Professor 

 Semper, and is now universally acknowledged. But my other 

 conclusion has not gained the same acceptance. Coincidently with 

 the communication to which I have last referred, it was affirmed by 

 Professor Greef of Marburg and by Dr. Ludwig, that the real nerve 

 in the arms of Crinoidea is (as in other Stellerida), a fibrillar band 

 (fig. 1, in-) that lies beneath the epithelial floor (ae)of the ambulacral 

 (ventral) furrow of the arms; a conclusion at which Professor Huxley 

 had independently arrived. And this view is now very generally 

 received and taught in Germany. 



In a third communication which I shortly afterwardsf made to the 

 Royal Society, I referred to this doctrine ; and, whilst admitting the 

 probability that this sub-ambulacral band is really a nerve, I adduced 

 what seemed to me conclusive proof that it cannot be the nerve 

 through which the motor apparatus of the arms is called into action. 

 For, in the first place, it is far removed from this apparatus in 

 position ; being separated from the muscles by the triple canal-system, 

 and not being connected with them (so far as can be discerned) by 

 any branching fibres. And, further, the loss of the visceral mass 

 (which contains the central ring of this ambulacral nerve-system) 

 was not found in the least degree to interfere with the rhythmical 

 swimming actions of the animal ; whilst a division of the ambulacral 

 nerve in any individual arm produced no paralysis of that arm. 



On the other hand, I stated that my son (who was then working in 

 the laboratory of Professor Semper at Wiirzburg) had fully confirmed 

 " Proceedings," Jan. 20, 1876, p. 226. 

 t Ibid., April 6, 1876. 



