ON TIIE ZOOLOGICAL STATION AT NAPLES. 257 



who hare discussed the question, maintain that the real nervous system 

 of Autedon consists of the ' subepithelial bands,' which run along the 

 ventral surface of the arms and disc, immediately beneath and in very 

 close relation with the ciliated epithelium lining the ambnlacral grooves. 

 Ludwig and those agreeing with him rely mainly on the close resem- 

 blance, or actual identity, in histological structure and in relation to the 

 overlying epithelium between these subepithelial bands and the ambn- 

 lacral or radial ' nerves ' of the starfish, and hold that if the homology 

 of these two structures bo admitted, it is extremely difficult to conceive 

 that Crinoids can have in addition to thi3 normal Echinoderm' nervous 

 system an additional one — i.e., the axial cords and the central capsnle 

 from which they spring — which is altogether unknown and unrepresented 

 in other Echinoderms. 



The Carpenters accept the nervous character of the subepithelial 

 bands, but maintain that they form but a small and comparatively subor- 

 dinate part of the entire nervous system. 



My own investigations consisted of an experimental examination of 

 the functions, (a) of the central capsule, (b) of the axial cords, and (c) 

 of the subepithelial bands. I employed both mechanical and chemical 

 irritation as sources of stimulation, and limited the action of the irritants 

 to the desired point by removal of the surrounding parts either mechanically 

 or by means of strong nitric acid. 



Concerning the central capsule, I find that so long as this remains 

 intact and in connection with the axial cords, the animal retains the power 

 of co-ordinated movements of the arms, as shown by the normal swimming 

 movements, and by the tendency to right itself when placed in a tank 

 wrong way up — i.e., with the oral surface downwards. This power of co- 

 ordinated movements is not affected by removal of the entire visceral 

 mass, an operation which involves the complete isolation of the subepi- 

 thelial bands of the several arms from one another. On the other hand, 

 removal or destruction of the central capsule, if thoroughly performed, 

 causes complete and permanent loss of the power of co-ordinated move- 

 ments. I therefore conclude that the central capsule is the centre 

 governing these movements. 



Concerning the axial cords, I find that irritation of them causes active 

 flexion of the arm affected, and also of the other arms, provided the com- 

 munications of the central capsule with the axial cords be intact. 



Division of the axial cord of an arm causes complete physiological 

 separation between the parts on opposite sides of the injury, even though 

 the subepithelial band be carefully preserved. From my experiments on 

 the axial cords, which were very numerous and varied, I conclude that 

 they are the real nerves, both motor and sensory, of the arms. 



Concerning the subepithelial bands, I find that, while certainly nervous 

 in structure and presumably in function as well, they are of very sub- 

 ordinate importance. The effects of irritation or destruction of them are 

 almost confined to the tentacles bordering the ambulacral grooves, with 

 which they are in very intimate relation. 



_ Concerning the morphological difficulty involved in the possession by 

 Crinoids of an antambulacral, in addition to the normal ambulacral nervous 

 system of Echinoderms, I would submit the following considerations. 

 The nervous system of an Asterid is not confined to the radial ambulacral 

 bands and their connecting oral commissure, but can be traced over the 

 tube feet, and also over the dorsal or antambulacral surface of the animal. 



1884. s 



