416 THE VOYAGE OF H.M.S. CHALLENGER. 



perisome of the arms and disk. Jickeli says, for example, " von diesem dritten Nerven- 

 centrum gehen auch starke Zweige in die ventrale Korperhaut uud liisen sich dort in feine 

 nervose Geflechte auf.'" It wUl be strange indeed if these prove to be anything else 

 than the ramifications of the ventral branches of the axial cords of the arms which I 

 described long ago as extending to the edges of the food-groove (see fig. 4, p. 113 ; fig. 5, 

 p. 121 ; and fig. 8, p. 123). I cannot say, however, that I have ever seen the pentagonal 

 rino- round the mouth W'hich Jickeh mentions, nor even its radial extensions at the sides 

 of the water- vessels ; unless indeed these last be the lateral trunks which I have described 

 above in Actinometra iiigi'a, from sections now nearly nine years old (p. 122). 



The branches of Jickeli's third nervous system which break up into a plexus in the 

 ventral perisome appear to me to be identical with those which I described two years ago 

 as extending along the sides of the ambulacra of Antedon eschrichti from the edge of the 

 disk to the neighl)ourhood of the mouth.^ A diagrammatic representation of them is 

 given on p. 123, while illustrations of single sections, both of this species and oi Penta- 

 crinus decorus, are shown on PI. LIX. figs. 2-7. These branches are unquestionably of 

 the same nature as those occupying a similar position in the arms (PI. LX. fig. 6, a'), and 

 belong like them to the system of the central capsule and axial cords, vdth which last 

 they are connected at the edge of the disk. But at the same time I fully believe that 

 they are the peripheral portions of the third nervous system described by Jickeli. The 

 so called papillae of the tentacles have also attracted his attention, and he regards them 

 as .sense-organs of a somewhat complicated nature, supporting fine sensory hairs. He 

 thus inclines to Perrier's view of the nature of these papiUge rather than to that of 

 Ludwig, who regards them as glandular organs. Jickeli, however, describes them as being 

 innervated by the branches of his third nerve-centre ; while according to Perrier ^ they 

 receive nerve-fibres from the ventral branches of the axial cords, which form what I have 

 called the parambulacral network. But if I am right in identifying this with the 

 peripheral part of Jickeli's third nervous system, his observations are completely in 

 accordance with those of Perrier. 



1 Zool. An::eiger, vol. vii. p. 369, 1884. - QimH. Journ. Mia: Sci., 1883, vol. s-viii., N. S., p. 615. 



' Comptes rendus, t. xcvii. p. 188. 



