EOSACEUS, LINCK (COMATULA EOSACEA OF LAMAECK). 
525 
distinct central depression, and the raised external rim indicates a division into five 
crescentic lobes. 
The whole cup gradually expands and increases in size. The five basal plates enlarge 
and become more definite in form. Their upper edges are still irregular in outline, 
somewhat crescentic, arching upwards towards the bases of the orals ; but the lateral 
edges are now bounded by smooth straight calcareous bands, the sides of each plate 
applied with the intervention of a narrow band of sarcode to the similar edges of the 
two contiguous plates. The narrow lower edges of the basals are rough and irregular, 
resting on the upper surface of the irregular ring-like rudiment of the centro-dorsal 
plate. The oral plates likewise undergo a change in form. They become wider infe- 
riorly, and the sides of the plates towards the lower margin curve outwards, the lower 
borders thus becoming concave, the convexity turned inwards towards the centre of the 
body. At the same time the upper edges, which remain narrow and rounded, curve 
slightly forwards and inwards towards the opening of the cup. If the animal remain 
undisturbed in well aerated water, when the development of the skeleton has reached 
this stage, the five lobes (the “ oral lobes”) forming the edge of the calyx gradually 
expand, till the cup assumes the form of an open bell (Plate XXVI. fig. 1). Imme- 
diately on opening, at least five, and more usually fifteen, delicate, extremely extensile 
tentacles are protruded from the cup. The mouth, with the organs immediately 
surrounding it, is formed even before the separation of the oral lobes. It may be seen 
occupying the centre of the cup (Plate XXVI. fig. 3) immediately after its expansion, 
as a large patent aperture. When the cup is fully expanded, the transparent tissue 
continuous with the five oral lobes, and forming the margin of the disk, seems to curve 
over uniformly into the wide funnel-shaped central opening. The mouth, however, 
frequently contracts, though it never appears to close completely ; and when contracted 
it is bordered by a slightly thickened very contractile rim, which projects over the cavity 
of the oesophagus and forms an imperfect sphincter. When this sphincter is relaxed 
and the mouth fully open, it is easy to see down to the very bottom of the digestive 
cavity, a sac-like space apparently simply hollowed out in the general sarcode-body 
(Plate XXVI. fig. 3). 
Commencing immediately within the mouth, a series of irregularly-lobed glandular 
masses, of a pale yellowish-brown colour, project into the cavity of the stomach, curving 
in an irregular spiral down to the bottom of the cup. These glandular folds are richly 
clothed with long vibratile cilia. The merest film of sarcode separates their secretion 
from the stomach-cavity. The slightest touch, even of a hair, ruptures them and causes 
the effusion of a multitude of minute granules, some colourless and transparent, and 
others of a yellow or brownish hue. There can be little doubt from their position and 
colour that these lobes form a rudimentary liver. They appear very early in the penta- 
crinoid, colouring the lower portions of its body in the earlier stages of its growth within 
the pseudembryo. They increase steadily in bulk during its later stages, and with but little 
change of character make up a large portion of the visceral mass in the adult Antedon. 
