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 und losen sich dort in feine 
nervose Geflechte auf.”! It will 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 
ring round the mouth which Jickeli 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 nigra, 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 neighbourhood of the mouth.’ A diagrammatic representation of them is 
given on p. 123, while illustrations of single sections, both of this species and of Penta- 
crinus decorus, are shown on Pl. LIX. figs. 2-7. These branches are unquestionably of 
the same nature as those occupying a similar position in the arms (Pl. LX. fig. 6, a’), and 
belong like them to the system of the central capsule and axial cords, with 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 papille 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 papille 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 
étccordance with those of Perrier. 
1 Zool. Anzeiger, vol. vii. p. 369, 1884. 2 Quart. Journ. Mier. Sci., 1883, vol. xxiii., N.8., p. 615. 
3 Comptes rendus, t. xcvii. p. 188. 
