CRINOIDEA. 267 
a rose with five petals. At the base of the stem of this animal-plant, 
in many of the Crinoidez, we find a sort of spreading root, which is 
implanted in the rocks, and is capable of growing by itself, and 
of nourishing the stem. 
The root and stem of the fixed Encrinites seem to indicate that 
the animal can only live with the headerect. Their normal condition 
is thus quite different from that of any other of the Echinoderms, 
almost all of which keep their mouths invariably directed downwards. 
Pentacrinus and Rhizocrinus are chiefly found on rocky beds, or 
in the midst of banks of corals, at greatdepths. There, firmly fixed 
by their roots, their long stems raise themselves vertically; then, 
with expanded calyx and long-spreading arms, they wait for the prey 
which passes within their reach in order to seize it. 
The Pentacrinus caput Meduse has, as we have said, been fished 
up from great depths in the Antilles. It is borne upon a stem of 
from eighteen to twenty inches in height, terminating in long movable 
arms, the internal surface of which bears the ambulacral feet. In 
the middle of the arms is a mouth, and at the side the orifice for the 
expulsion of the digested residuum. 
The Crinoidez are not, however, all like the two species which 
have been referred to. There is an entire section of the animals belong- 
ing to this class, namely, the Comatulide, which are fixed in their early 
days, but separate themselves from the rooted stem in their adult 
age, and, throwing off the bonds imposed in their youth, live freely, 
swimming through the water, or clinging to mussel or oyster banks. 
Species of the genus Comatula are found in the seas of both hemi- 
spheres. Their bodies are flat—large calcareous plates form a cuirass 
upon their backs—presenting, besides, cirri composed of numerous 
curling joints, the last of which terminates in a hook. ‘The ventral 
surface presents two orifices : the one in the centre corresponding to 
a mouth, the other evidently intended for the discharge of the pro- 
ducts of digestion. This animal is provided with five arms, which 
diverge directly from the centre plate or cuirass. The branches of 
these arms have a double row of ambulacral feet, in the centre of 
which is the ambulacral groove, properly so-called. The feet are 
clothed with vibratile cilia over their whole surface. These cilia 
guide the current which drives the substances on which the animal 
feeds—such as the organic spores of sea-weeds and microscopical 
animalcules floating in the sea—towards its mouth. 
The movements of these curious creatures are very slow, their 
only object being to catch the bodies of animals and marine plants, 
“or, by extending or contracting their arms, to feel their way through 
