1884.] On the Nervous System of the Crinoidea. 71 



Crinoids. Moreover, in the dorsal cirri of Comatulidae, which have a 

 markedly prehensile power, but have no definite muscular bundles, 

 the axial cords send branches into the contractile substance that 

 serves the purpose of muscles. Branches of the axial cords (a, a) 

 also proceed to the lateral surfaces of the soft parts that lie on the 

 ventral side of the arms and pinnules, and are traceable to the very 

 lips of their ambulacral grooves, forming also an. extensive plexus 

 along the sides of the ambulacral grooves of the disk. On the other 

 hand, the sub-ambulacral nerves, which in Ophiurida- send Very 

 distinct branches to the muscles of the arms, send no such branches 

 to the arm-muscles of Crinoidea. And thus the evidence furnished 

 by anatomical distribution as to the source of the nerve-power which 

 calls those muscles into contraction, is alike positive in regard to the 

 axial cords, and negative in regard to the sub-ambulacral nerves. At 

 the same time, the distribution, of the branches of the axial cords to 

 the perisome of the soft parts of the arms and pinnules, would indi- 

 cate that these have an afferent or sensory function.* 



Physiological Evidence. The inquiries of Dr. P. H: Carpenter, 

 having been entirely limited to the anatomical examination of spirit 

 specimens of Crinoidea, do not afford any direct confirmation of the 

 statements I formerly made as to the actions of living Antedons ; 

 but they furnish most remarkable confirmatory evidence of an 

 indirect kind tbat, namely, which may be deduced from what 

 Cuvier termed " Experiments prepared for us by Nature." For having 

 met with numerous cases in which the ambulacral groove and the 

 tentacular apparatus are wanting, whilst the arms and pinnules 

 showing this deficiency are normally constructed in other respects, 

 he has invariably found that the ventral or sub-ambulacral nerve is 

 alike deficient, while the axial cord and its branches have their usual 

 distribution. Among these cases, the following may be specified : 



a. The long pinnules which come off from the second brachial 

 segments of Antedon rosacea, and which (from the manner in which 

 they arch over the mouth during life) have been distinguished as 

 oral pinnules, are destitute of the tentacular apparatus as I pointed 

 out in my original Memoir ( 16). This peculiarity has been found 

 by my son to be a general character of the genus Autedon ; and he has 

 further shown that, with the deficiency of tentacles, there is also an 

 absence of the ordinary ciliated epithelium of the ambulacral groove, 

 and of the subjacent nerve and nerve-vessel. f 



* The observations^ Dr. P. H. Carpenter upon the distribution of the branches 

 of the axial cords, have been fully confirmed by those of M. Edmond Perrier ; 

 who lias been led by his own independent investigations on Antedon rosacea to the 

 fall acceptance of the nervous character of these cords, notwithstanding his opposite 

 prepossession. (See " Comptcs Rendus," July, 1883, tome xcrii, p. 187.) 

 f ' Journal of Anatomy and Physiology," vol. xi, October, 1876, p. 89. 



