1884.] On the Nervous System of the Crinoidea. 73 



in the muscular bundles and perisomatic surface, have to account for 

 these two facts in the ordinary life-history of uninjured animals : 

 first, the immediate and consentaneous contraction of the hundreds 

 (or thousands) of arm-muscles in Antedon, called forth by irritation 

 of the oral pinnules ; and, secondly, the performance of swimming 

 movements as regular as those of Antedon, by the non-tentaculated 

 arms of Actinometree notwithstanding the absence, in both cases, of 

 what is affirmed to be their sole nervous supply. 



Thus, while the doctrine that the remarkable sensori-motor endow- 

 ments of the Crinoidea depend upon their ventral nervous system, 

 consisting (as in Asterida and Ophiurida) of an oral ring with 

 radial branches, is supported only by a theoretical homology, it is in 

 direct contradiction to the following facts : 



1. The absence of any branches from the sub-ambulacral nerves to 

 the muscular apparatus of Crinoidea generally. 



2. The absence of sub-ambulacral nerves from those pinnules of 

 Antedon which are most distinguished by their sensory endowments. 



3. The absence of sub-ambulacral nerves from a large proportion of 

 the arms of Actinometree, which, nevertheless, take their full share 

 in the co-ordinated swimming movements of those animals. 



4. The continued performance of these movements by Antedons 

 from which the whole visceral mass, including the oral ring, has been 

 removed, and by arms whose sub-ambulacral nerves have been cut 

 near their base. 



On the other hand, the dependence of the general sensori-motor 

 endowments of Crinoidea upon what I have described as their dorsal 

 nerve-system, is a doctrine which has been found to harmonise 

 alike with every fact that the most careful and minute study of their 

 organisation has brought to light, with the results of the " Experi- 

 ments.prepared for us by Nature" in the varieties of that organisa- 

 tion, and with those of such experiments upon the living animals as 

 would be deemed conclusive in other cases. It is opposed only 

 by a theoretical homology, a preconceived notion of what Crinoids 

 ought to be,* which was adopted (as Dr. P. H. Carpenter has perti- 



* Thus Baudelot, who was searching for the nervous system of the Crinoidea, 

 and traced out the whole system of dorsal cords with their pentagonal commissure 

 (apparently in ignorance of what I had previously done), while remarking that 

 " dans leur disposition aussi bien que dans leur structure ces parties offrent une 

 analogic presque complete avec les cordons nerveux des autres iSchinodermes," 

 nevertheless affirms that " evidemment elles n'appartiennent point au systime 

 nerveux." (' Archiv. de Zool. Exper. et Gen.," tome i, p. 211.) 



[Since the above was written, Dr. P. H. Carpenter has drawn my attention to a 

 recent paper by Dr. Weinberg on the Morphology of living Crinoids (" Der Natur- 

 historiker," Mar. Jun., 1883, pp. 266 307), in which Dr. P. H. Carpenter's 

 descriptions (with illustrative figures) of the muscular branches of the radial cords 

 lire treated as " suppositions ; " while his account of the absence of tentacles, of the 



