74 Dr. W. B. Carpenter. [May 29, 



nently remarked) without any sufficient knowledge of the anatomy 

 of this most interesting group. Further, that this dorsal nerve- 

 system is the fundamental and essential sensori-motor apparatus of 

 Crinoidea, and that their ventral nerve-system is secondary and 

 accessory, is indicated by the universal presence of the former in 

 every arm and pinnule, while the -latter is frequently absent. And 

 that the function of this latter is limited to the control of the tenta- 

 cular apparatus, appears probable from the constancy of its associa- 

 tion with that apparatus ; being invariably present in those arms and 

 pinnules which are provided with tentacles, and absent in those which 

 are destitute of them. 



In conclusion, I would remark that the question whether these 

 axial cords do or do not constitute parts of the fundamental nervous 

 system of Crinoidea, is one of far-reaching interest ; since it obviously 

 affects our whole conception of the morphology of the group. If I 

 am right in my contention, the centre of the nervous system of the 

 Crinoidea has its seat in that Stem which is the most distinctive 

 feature of their structure. For the quinquelocular organ that lies 

 in Antedon within the centro-dnrsal basin, is only an expansion of 

 the soft axis which occupies the central canal that extends through 

 the entire length of the stem; repeating on a larger scale a similar 

 dilatation that occurs at every node from which a circlet of cirri is 

 given off. And the radial skeleton of the stem, of the calyx, of the 

 arms, and of the pinnules of a Crinoid, is even more completely built 

 up on this elongated nerve-centre and its radial extensions, than is 

 the longitudinally segmental skeleton of a Vertebrate animal upon its 

 cranio-spinal axis, a consideration which must be constantly kept 

 in view in any attempt to trace out the homologies of Crinoidea 

 with other Echinodermata. To myself it has always appeared that 



ambulacra! epithelium, and of the ventral nerve, in a large proportion of the arms of 

 Actinometra, ia altogether ignored. As Dr. Weinberg seems to justify his disbelief 

 of Dr. P. H. Carpenter's description, by his own failure, and that of Dr. Ludwig, to 

 verify them on Antedon rotacea, it may be well for me to state that its accuracy 

 has been verified by careful examination of Dr. P. H. Carpenter's preparations, not 

 only by myself, but by many other experienced Microscopists in this country ; 

 whilst, as already mentioned (p. 71, note), Professor Perrier has been led by his 

 own independent investigations to accept my own and my son's statements as fully 

 borne out by microscopical evidence. As Dr. Weinberg, though he has had the 

 opportunity of studying Antedon rosacea alive, and of thereby refuting my experi- 

 mental results, if erroneous, refrains from discussing them, and as he also ignores 

 the fact (though vouched for by Ludwig) that the ventral nerve is wanting iu the 

 peculiarly sensitive oral pinnules of Antedon, it seems as if his confidence in his 

 theoretical Morphology blinds him to every fact which conflicts with this. Tl 

 complete confirmation of my experiments by Professor A. M. Marshall and Dr. Car 

 F. Jickeli (see ADDENDA) may perhaps render them worthy of his more serioi 

 consideration (June 28).] 



