ON Tin: zoui.ooic.vL station at Naples. 



•J 07 



, ami 

 tbcro 

 jcn in 

 rated, 

 i; tlio 

 to bo 



wliicli 

 it two 

 circlot 

 jiisclos 

 !iliii(*Hl 

 isclvos 

 ;3 until 

 lin, and 



I WilS, 



ure. 

 inculn.^, 

 onnd to 

 ikosttM'. 

 the ox- 



auneliil 

 roscopic 



lalopodii, 

 to miiko 



|o till tho 

 Uvith (") 

 la fuvtlun- 

 it of the 

 ^branclis. 

 ■ouvable ; 

 limited 

 [to othci' 

 nervous 

 lie points 

 Itlier, tlic 



ited tliat 

 Ithe arms 

 |iew, and 



liical and 

 who has 



Is favour, 



Ll writers 



\n1\o Imvo (lis( nssc'd tho (lucstlon, nmiiitain that tho real nervous system 

 ol' Antcdon ei>n.sists of tlic ' snl)L'|)itIielial bainls,' wliit'h run aloiu' tlio 

 ventral si'"faeo of tho arms and dise, inimediatoly beneath and in very 

 close relation with tho cilialcd cpithehiini iiiuiiff the ambniacral <,''roov((s. 

 liudwif^ and those a^reeini,' with him rely mainly on tho close resem- 

 hlanee, or actual identity, in histolo^'ical strnctnro and in relation to tiio 

 overlyin<^ epithelium between these Md.'epithelial band-i and tho ambii- 

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

 of these two structures be admitted, it is extremely dillieult to coucoivn 

 that Crinoids can have in addition to this normal lOchinoderm norvons 

 system an additional one — /.c, the axial cords and tho eetitr.d ciipsnlo 

 from which they spriii<i^ — which is altogether unknown and unrepresented 

 in other Kchinodeinis. 



Tho Carpenters accept the nervous character of the subepithelial 

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

 dinate part of the entire nervous systeni. 



^ly own investigations consisted of an experimental examination of 

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

 of the 8ubo])ithelial bands. I oaiployed both mechanical and chemical 

 irritation as sources of stimulation, and limited the aetioii of tlic irritants 

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

 or by means of strong nitric acid. 



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

 intact ami 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 ])laced in a tank 

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

 ordinated niovementg is not atfected by removal of the entire visceral 

 inasp, an operation which involves tho com[)leto isolation of the subepi- 

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

 removal or destruction of the central ca])Sulo, if thoroughly ])erformed, 

 causes complete and permanent loss of tho 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 centi'al cai^sule with the axial cords be intact. 



Division of the axial cord of an arm causes complete phyrsiological 

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

 the subepithelial band be carefully preserved. From my experiments on 

 the axiril 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 effect" '^f irritation or destruction of them are 

 almost confined to the tentacles rdering the ambniacral grooves, with 

 which thoy are in very intimate relation. 



Concerning the morphological difficulty involved in the possession by 

 Crinoidsof an antambulacral, in addition io the normal ambniacral nervous 

 system of Echinoderms, I would submit the following considerations. 

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

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

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



1881. S 



