Anatomy of C.omatula. 207 



probably having the functions of nerves, though not exhibiting 

 their characteristic structure." 



Again, in describing the dorsal cirrhi (par. 29), the axial 

 canal of the arms (par. 45), and the circlet of basals in the 

 Pentacrinoid larva (par. 76) , I mentioned the connexion of these 

 solid sarcodic cords with " the wall of a remarkable quinque- 

 locular organ, contained within the centro-dorsal basin," which 

 organ was " supposed by Prof. Miiller, who first noticed its 

 presence [though he did not recognize its subdivision], to be a 

 heart," but which " I shall hereafter describe under the name 

 of the ' centro-dorsal vesicle,' and which I shall show to be 

 an expansion of the original crinoidal axis, hollowed out into 

 a multiple ventricular cavity." 



The chief difficulty which I felt in regarding this axis and 

 its extensions into the arms as constituting a Nervous System, 

 arose from the entire absence of any of the ordinary histological 

 characters of nerves. I found that I could tear the axial cords 

 (hardened in strong spirit) into fibrils of extreme minuteness, but 

 that these fibrils showed a perfectly homogeneous composition. 

 Still "the remarkable energy and rapidity of muscular action in 

 Comatula, far surpassing that of every other known animal of 

 its class " (par. 19), strongly impressed me with the belief that 

 its muscles must be called into action by nerves proceeding 

 from a common centre ; and as these muscles are all flexors, 

 while the extension of the arms is provided for by elastic liga- 

 ments, I arrived at the opinion that the want of histological 

 differentiation in the nervous system might be related to the 

 fact of its having only one kind of action to perform. To this 

 conclusion I have given expression in the last edition of my 

 ' Microscope and its Revelations,' p. 771. 



Being at Oban in the summer of 1867, I made an experi- 

 ment on the living Comatula, which seemed conclusive (not 

 only to myself, but to the numerous Physiologists to whom I 

 have mentioned it) as to the nervous character of the central 

 quinquelocular organ and of the cords proceeding from it. 

 Having turned out from the calyx the whole visceral mass 

 (which, in the living animal, is so loosely held in by the soft 

 perisome as often to be lost in the dredge), I had remaining the 

 entire skeleton, its muscles and ligaments, and the supposed 

 nervous system radiating from the central quinquelocular organ 

 still contained in the cavity of the centro-dorsal plate. On 

 irritating the central organ by a needle passed down through 

 the aperture leading into this cavity from the base of the calyx, 

 all the ten arms suddenly and consentaneously coiled up. On 

 the withdrawal of the needle, the arms gradually straightened 



15* 



