REPORT ON THE CRINOIDEA. 117 



with what we know of their origiu ; and it likewise fails to account for their relations in 

 the adult Crinoid. If this fibrillar tissue were limited to the skeleton, there might be 

 some reason in Ludwig's suggestion. But it gives no rational explanation whatever for 

 the extension of branches from the axial cords of the skeleton through the perisome of 

 the disk and arms, up to the bases of the tentacles at the sides of the food-groove 

 (Figs. 4-7, a'. Fig. 8 ; PL LIX. figs. 2-4, 6, 7 ; PL LX. fig. 1—ad ; PL LX. fig. 6, a'), and 

 even as asserted by Perrier, into the tactile hairs l^orne by these tentacles.^ 



Ludwig's theory too entirely fails to account for the elaborate arrangement of 

 commissures which one finds in Comatula and Pentacrinus (PL XXIV. figs. 7-9 ; 

 PL LVIII. figs. 1-3), and in a less degree in Bathycrinus (PL Vllb. fig. 4, ceo), 

 Rhizocrinus (PL Villa, fig. 6, ceo, ico), and Encrinus. Why should the first 

 radials and the axillaries be in such special need of nutrition that the former should 

 possess both interradial and intraradial commissures, and the latter no less than 

 fovir cords, to say nothing of the transverse commissure ? Five radial cords starting 

 directly from the envelope of the chamljered organ would surely serve aU the necessary 

 purposes of nutrition. As it is, however, each ray and indeed each arm is supplied by 

 fibres from two of the primary interradial trunks. This complex arrangement receives 

 no explanation whatever on Ludwig's theory, though it is easily understood if we suppose 

 that the axial cords are the means by which co-ordinated impulses reach the muscles 

 from a governing centre. 



Their anatomical structure also favours this view. In a paper which was published 

 some years before the discovery of ambulacral nerves in tlie Crinoids, Baudelot quoted 

 MiiUer's description of the so-called arm-nerve {i.e., the genital cord), and apparently 

 adopted it as correct.^ But he also stated that he could not help being struck with the 

 resemblance " qui existe entre la structure du cordon fibreux central des bras et la cordon 

 nerveux des autres Echinodermes." He described its relations pretty accurately, and 

 then proceeded to say " Ainsi done chez les Comatules il existe des parties qui e\ddemment 

 n'appartienuent point au systeme nerveux, et qui dans leur disposition aussi bien que 

 leur structure ofirent une analogic presque complete avec les cordons nerveux des autres 

 Echinodermes." 



I do not know what reason Baudelot may have had for his conviction that the axial 

 cords are evidently not of a nervous nature, unless he had implicitly accepted Miiller's 

 account of the nervous system of a Crinoid. A very little troul)le, however, would have 

 convinced him that this was totally incorrect. In fact Dr. Carpenter had referred to 

 MiiUer's error four years before the publication of Baudelot's observations, and had also 

 mentioned that he had reasons for regarding the branching fibres proceeding from the 

 axial cords to the muscles as probably having the function of nerves. Had Baudelot 



' Comptus rendus, t. xcvii. p. 188. 



2 Contribution k rhistoire du systJjme nerveux des :6chinoJerme3, Archives d. Zool. exp^r., t. i. p. 211. 



