108 DR. WILSON ON THE NERVOUS SYSTEM OF THE ASTERID.E. 
vertebral spaces, most likely to be distributed to the vesicles of the feet and the peritoneal 
covering of the csecal chamber. 
The nerve-cord terminates at the distal end or point of the ray, in a bulbous swelling 
coloured with different shades of red pigment and forming the eye-spots. Erom the 
cells lying immediately above the eye-bulb, filaments pass more or less obliquely down- 
wards to the pigment-masses of the eye, termed cones by Haeckel. These eye- spots, as 
Haeckel has pointed out, consist of pigment-cones, each containing a globular lens, and 
having their bases directed towards the cornea. 
Though the nerve-cells do not apparently pass beyond the eye-spot, yet a great number 
of their filaments extend further, to a curious contractile organ resembling, in many 
points, one of the suckers, and, most probably, performing the function of a tactile organ. 
The root of the eye-bulb rests upon the base of this tactile organ, and can thereby be 
moved about tolerably freely. 
The nerve-cords, connecting the ganglia, are about half the thickness of the ambulacral 
cords, these latter splitting into two pretty equal portions. They lie in close proximity to 
the vascular perioral ring connected with the heart. Nerve-cells are found in them, though 
it is difficult to detect the relation of these to the filaments. Some of these filaments 
pass towards the mouth, while others are directed outwards. These nerve-cords are con- 
sidered by Tvliiller as simply the connective media, by means of which the motions and 
actions of the animal are harmonized. He supports this view by stating that those Star- 
fishes which break themselves to pieces on being handled, may be prevented from doing 
so if these cords are snipped through with a pair of scissors. 
The above is a general view of the nervous system of the Asteridse. We now proceed 
to consider in detail the species examined. 
1. Solaster papposa. 
This species is the best-adapted for making a microscopic examination, because it pre- 
sents the most simple structure. Unfortunately, however, it cannot be preserved long 
alive in confinement, as it soon dyes the water with its pigment. 
The ambulacral cord is easily reached, lying in the wide ambulacral groove, and flanked 
on either side by the single rows of comparatively thick suckers. The vertebrae forming 
the groove for the nerve- cord and feet are few in proportion, widely separated, and but 
loosely connected with one another. On a transverse section of the ray, they appear as 
broad, irregular-shaped, calcareous plates, resting against one another along a certain 
extent of their internal margins *. Tor convenience of description we may divide each 
plate into a vertical portion extending from x to <?, and an oblique from x to d. The ver- 
tical portions are not equally in contact throughout their extent, but diverge above, owing 
to the bevelling off of their margins. The triangular space thus formed is filled up by 
fibrous tissue, which, for distinction, may be termed the superior ligament ic). The 
oblique portions of the plates pass off laterally more or less widely from each other 
according to the condition of the animal. Its ventral nianrin, or that turned towards 
* See Plate XIII. fig. 1. 
