758 
ZOOLOGICAL LITERATURE. 
Tlie upper surface of the aims now becomes gTooved by the development, 
on either side of the central vessel, of a series of delicate crescentic leaves. 
These leaves are hollow, communicating by special apertures with the radial 
vessel, and lilled with fluid from it. At the base of each of the leaves there 
is a pair of tentacles forming a group Avith the leaf, and along with it com- 
municating with tlie vessel. One of these tentacles (the distal one) is some- 
what larger than the proximal ; they are both slightly club-shaped, the club- 
shaped extremity fringed on cither side with conical papillie. They are 
non-extensile, and resemble in every particular the ten non-extensile ten- 
tacles early developed from the oral ring. A group consisting of a crescentic 
leaf and two non-extensile tentacles lies immediately at the base of each ex- 
tensile tentacle, and a little lower down the arm. Minute spicules, some of 
them simple or key-shaped, and others expanding into a cribriform film, appear 
in the superficial sarcode-lajm’ along the back or edges of the arms j and, 
usually at the base of each of the tentacles, irregularly imbedded in the sar- 
code-substance, there is one of the calcareous glands. 
Immediately on the expansion of the equatorial portion of the cup, the 
wall of the stomach becomes separated, by a distinct body-cavity filled Avitli 
fluid, from the body-Avall. The stomach seems to hang in this cavity as a 
separate sac, attached to the body-wall here and there by sarcodic bands and 
threads. As the disk expands, the radial canal may be distinctly seen, rising 
from the oral ring, crossing the narrow disk, and running along the upper 
surface of the arm, communicating on either side with the various tentacles 
and respiratory leaves, and ending at the extremity of the arm in the azygous 
tentacle, lieneath the radial canal a tubular extension of the perivisceral 
space passes along the radial grooves. This series of vessels, for which Dr. 
Carpenter proposes the term ‘‘ coeliac canals,” afterwards extends through- 
out the whole length of the arms. In the mature Antedon Dr. Carpenter 
has observed a third vessel, intermediate between the coeliac and tentacular 
canals j but no trace of this vessel can be detected in the earlier stages in the 
development of the pentacrinoid. 
A little later, the end of the arm shows a tendency to bifurcate, and two 
half rings, with their enclosed sheaA^es of calcified tissue, give the first indi- 
cation of the first tAvo brachials. At the stage described, the arm is free 
from the base of the second radial ; at a later stage the visceral sac extends 
to the bifurcation, and the Avliole of the radial portion of the arm becomes 
included in the cup and disk. The azygous tentacles go no further than the 
bifurcation. They remain for some time in the centre, betAveen the tAvo 
divisions of the arm, while secondary branches from the radial canal run on 
in the brachial grooves. About the period of the development of the second 
radials, a forked spicule makes its appearance in one of the interradial spaces 
betAveen the upper portions of tAvo of the first radial plates. This gradually 
extends in the usual Ava}^ till it becomes developed into a round cribriform 
superficial plate. 
Simultaneously Avith the appearance of this anal ” plate, a cjecal process, 
like the finge*!* of a glove, rises from one side of the stomach and curves 
towards the plate. The plate increases in size, becomes enclosed in a little 
flattened tubercle of sarcode, and maintaining its upriglit position it passes 
slightly outAvards, leaving a space on the edge of the disk between itself and 
the base of the oral plate immediately Avithin it. 
