NOTES ON THE OPIIIURANS, OR THE SAND AND BRITTLE STARS. 343 
ful pinching pedicellarhe as in the Urchins and Starfish. They 
do not help the star much in climbing up glass or weed, but they 
appear to be extremely sensitive to touch, to the presence of foul 
water, and of nice things. The large tentacles of the mouth 
angle spaces move much, and evidently direct food to the mouth, 
and when a soft bit of oyster is given to the animal, it being 
permitted to touch one of the arms, this is moved towards the 
mouth, and the mouth towards it. All the tentacles are expanded 
to the utmost, and the morsel is pressed against the mouth and 
gradually disappears, the opening between the teeth becoming 
slightly wider ; after awhile, the part of the food which cannot 
be digested is returned. They know what is nice, and can 
therefore taste ; they are vivacious after a good meal, and 
therefore digest comfortably ; their tentacles enlarge and con- 
tract, and the arms and body grow, therefore there must be 
a circulation and processes of nutrition. They have more than 
a rudimentary nervous system, but eye specks or visual organs 
are deficient. They soon die if their respiration is not well 
kept up ; and as this is mainly done by the tentacles and their 
internal machinery, a curious self-mutilation accompanies im- 
paired respiration. The arms are cast off at joint after joint, 
as the water becomes more and more impure. The Brittle Stars 
drop their arms, which continue to wriggle for a time very 
readily ; and the process of repair seems to be pretty rapid, for 
new arms or pieces soon grow again. 
It is now necessary to consider some points in their anatomy 
and physiology a little more closely. 
If the skin and scales of the middle of the upper part of the 
disc be carefully cut through and raised with a pair of forceps, 
a membrane will be found beneath them, and attached pretty 
firmly in some places and less so in others. The membrane is 
the upper part of the stomach ; and if it be opened, the inside 
of the organ is seen, and quite low down there are five whitish 
bodies projecting inwards towards a common point (fig. 5, d , e). 
These are the upper five teeth, one on each jaw, e, and the upper 
surface of the jaw plate and jaws is seen (fig. 9, e, ep , d). An 
opening exists between the approximating teeth centrally, and 
it leads to the lower surface of the animal, or to the lower 
opening of the mouth. The teeth stand out well, and the 
membrane of the stomach is not attached to them, for it en- 
circles the whole jaw arrangement a little further out than the 
attachment of the jaw plates to the jaws (fig. 5, s), and passes 
over the space between the angles. The stomach is in the 
shape of a wide-mouthed bag, which has no other opening 
than that of the so-called mouth, and it does not fill the body, 
nor is it, as in the star fishes, found in the arms. It is attached 
to the under surface of the skin of the upper part of the 
