Chapter II: Front Matter (2)

Grade A. PELMATOZOA.--Echinoderma with the viscera enclosed in a
calcified and plated theca, of which the oral surface is uppermost,
and which is usually attached, either temporarily or permanently, by
the aboral surface. Food brought to the mouth by a subvective system
of ciliated grooves, radiating from the mouth either between the
plates of the theca (endothecal), or over the theca (epithecal), or
along processes from the theca (exothecal: arms, pinnules, &c.), or,
in part, and as a secondary development, below the theca (hypothecal).
Anus usually in the upper or oral half of the theca, and never aboral.
An aborally-placed motor nerve-centre gives off branches to the stroma
connecting the various plates of the theca and of its brachial, anal
and columnar extensions, and thus co-ordinates the movements of the
whole skeleton. The circumoesophageal water-ring communicates
indirectly with the exterior; the podia, when present, are
respiratory, not locomotor, in function.

Class I. CYSTIDEA.--Pelmatozoa in which radial polymeric symmetry of
the theca is developed either not at all or not in complete
correlation with the radial symmetry of the ambulacra (such as obtains
in Blastoidea and Crinoidea); in which extensions of the food-grooves
are exothecal or epithecal or both combined, but neither endothecal
nor pierced by podia (as in some Edrioasteroidea) All Palaeozoic.

This class shows much greater diversity of organization than any
other, and the classifications proposed by recent writers, such as E.
Haeckel, O. Jaekel and F.A. Bather, start from such different points
of view that no discussion of them can be attempted here. Following
the narrative given above, we recognize a primitive
group--Amphoridea--represented by _Aristocystis_ (fig. 8). From this
are derived the orders Diploporita (fig. 9) and Rhombifera (fig. 10)
and the class Edrioasteroidea, all which have already been described
as steps in the evolution of the phylum. But there were also
side-branches leading nowhere, and therefore placed in separate
orders--Aporita and Carpoidea.

Order 1. _Amphoridea._--Radial symmetry has affected neither
food-grooves nor thecal plates; nor, probably, nerves, ambulacral
vessels, nor gonads. Canals or folds when present in the stereom are
irregular. Families: Aristocystidae (fig. 8); Eocystidae.

Order 2. _Carpoidea._--Theca compressed in the oro-anal plane and a
bilateral symmetry thus induced, affecting the food-grooves and,
usually, the thecal plates and stem. Food-grooves in part epithecal
and may be continued on one or two exothecal processes. No pores or
folds in the stereom. Families: Anomalocystidae, Dendrocystidae. These
correspond to Jaekel's Carpoidea Heterostelea; he also includes, as
Eustelea, our Comarocystidae and Malocystidae.

Order 3. _Rhombifera._--Radial symmetry affects the food-grooves and,
in the more advanced families, the thecal plates; probably also the
nerves and ambulacral vessels, but not the gonads. The food-grooves
are exothecal, i.e. are stretched out from the theca on jointed
skeletal processes (brachioles). These either are close to the mouth
or are removed from it upon a series of ambulacral or sub-ambulacral
plates not derived immediately from thecal plates, or are separated
from the oral centre by hypothecal passages passing beneath terminal
plates. The stereom and stroma become arranged in folds and strands at
right angles to the sutures of the thecal plates; in higher forms the
stereom-folds are in part specialized as pectini-rhombs. Families:
Echinosphaeridae; Comarocystidae; Macrocystellidae; Tiaracrinidae;
Malocystidae; Glyptocystidae, with sub-famm. Echinoencrininae,
Callocystinae, Glyptocystinae, of which examples are _Cheirocrinus_
(fig. 10) and _Cystoblastus_ from which Jaekel deduces the blastoids;
Caryocrinidae.

Order 4. _Aporita._--Pentamerous symmetry affects the food-grooves and
thecal plates; probably also the nerves and ambulacral vessels, but
not the gonads. Food-grooves exothecal and circumoral. The stereom
shows no trace of canals, folds, rhombs or diplopores. Family:
Cryptocrinidae.

Order 5. _Diploporita._--Radial symmetry affects the food-grooves, and
by degrees the thecal plates connected therewith, but not the
interradial thecal plates; probably also the nerves and ambulacral
vessels, but not the gonads. The food-grooves are epithecal, i.e. are
extended over the thecal plates themselves without intermediate
flooring; they are also prolonged on exothecal brachioles, which line
the epithecal grooves. The stereom of the thecal plates may be thrown
into folds, but the mesostroma does not so much tend to lie in strands
traversing the sutures, nor are pectini-rhombs or pore-rhombs
developed; diplopores are always present in the mesostereom, but often
restricted to definite tracts or plates, especially in higher forms.
Families: Sphaeronidae; Glyptosphaeridae, e.g. _Fungocystis_ (fig. 9);
Protocrinidae; Mesocystidae; Gomphocystidae.

The Protocrinidae lead up to _Proteroblastus_, in which the theca is
ovoid, sometimes prolonged into a stem, the plates differentiated into
(a) smooth, irregular, depressed interambulacrals, (b) transversely
elongate brachioliferous adambulacrals, to which the diplopores, which
lie at right angles to the main food-groove, are confined. This leads
almost without a break to the Protoblastoidea.

Class II. BLASTOIDEA.--Pelmatozoa in which five (by atrophy four)
epithecal ciliated grooves, lying on a lancet-shaped plate (? always),
radiate from a central peristome between five interradial deltoid
plates, and are edged by alternating side-plates bearing brachioles,
to which side-branches pass from the grooves. Grooves and peristome
protected by small plates, which can open over the grooves. The
generative organs and coelom probably did not send extensions along
the rays into the brachioles; but apparently nerves from the aboral
centre, after passing through the thecal plates, met in a circumoral
ring, from which branches passed into the plate under each main
food-groove, and thence supplied the brachioles. The thecal plates,
however irregular in some species, always show defined basals and a
distinct plate ("radial") at the end of each ambulacrum; they are in
all cases so far affected by pentamerous symmetry that their sutures
never cross the ambulacra. All Palaeozoic.

Division A. _Protoblastoidea._--Blastoidea without interambulacral
groups of hydrospire-folds hanging into the thecal cavity. Families:
Asteroblastidae, Blastoidocrinidae. The former might be placed with
Diploporita, were it not for a greater intimacy of correlation between
ambulacral and thecal structures than is found in Cystidea as here
defined. They form a link between the Protocrinidae and--

Division B. _Eublastoidea._--Blastoidea in which the thecal plates
have assumed a definite number and position in 3 circlets, as follows:
3 basals, 2 large and 1 small; 5 radials, often fork-shaped, forming a
closed circlet; 5 deltoids, interradial in position, supported on the
shoulders or processes of the radials, and often surrounding the
peristome with their oral ends. The stereom of the radials and
deltoids on each side of the ambulacra is thrown into folds, running
across the radio-deltoid suture, and hanging down into the thecal
cavity as respiratory organs (hydrospires).

These are the forms to which the name Blastoidea is usually
restricted. They have been divided into Regulares and Irregulares, but
it seems possible to group them according to three series or lines of
descent, thus:--

Series a. _Codonoblastida._--Families: Codasteridae, Pentremitidae
(fig. 13).

Series b. _Troostoblastida._--Families: Troostocrinidae,
Eleutherocrinidae.

Series c. _Granatoblastida._--Families: Nucleocrinidae,
Orbitremitidae, Pentephyllidae, Zygocrinidae.

Class III. CRINOIDEA.--Pelmatozoa in which epithecal extensions of the
food-grooves, ambulacrals, superficial oral nervous system,
blood-vascular and water-vascular systems, coelom and genital system
are continued exothecally upon jointed outgrowths of the abactinal
thecal plates (_brachia_), carrying with them extensions of the
abactinal nerve-system. The number of these processes is primitively
and normally five, but may become less by atrophy. The brachia rise
from a corresponding number of thecal plates, "radials (RR)." Below
these is always a circlet, or traces of a circlet, of plates
alternating with the radials, i.e. interradial, and called "basals
(BB)." Through all modifications, which are numerous and vastly
divergent, these elements persist. A circlet of radially situate
infrabasals (IBB) may also be present. Below BB or IBB there follows a
stem, which, however, may be atrophied or totally lost (see fig. 1).

The classification here adopted is that of F.A. Bather (1899), which
departs from that of Wachsmuth and Springer mainly in the separation
of forms with infrabasals or traces thereof from those in which basals
only are present. These two series also differ from each other in the
relations of the abactinal nerve-system. O. Jaekel (1894) has divided
the crinoids into the orders Cladocrinoidea and Pentacrinoidea, the
former being the Camerata of Wachsmuth and Springer (Monocyclica
Camerata, Adunata and Dicyclica Camerata of the present
classification), and the latter comprising all the rest, in which the
arms are either free or only loosely incorporated in the dorsal cup.
In minor points there is fair agreement between the American, German
and British authors. The families are extinct, except when the
contrary is stated.

Sub-class I. _Monocyclica._--Crinoidea in which the base consists of
BB only, the aboral prolongations of the chambered organ being
interradial; new columnals are introduced at the extreme proximal end
of the stem.

Order 1. _Monocyclica Inadunata._--Monocyclica in which the dorsal cup
is confined to the patina and occasional intercalated anals; such
ambulacrals or interambulacrals as enter the tegmen remain
supra-tegminal and not rigidly united. Families: Hybocrinidae,
Stephanocrinidae, Heterocrinidae, Calceocrinidae, Pisocrinidae,
Zophocrinidae, Haplocrinidae, Allagecrinidae, Symbathocrinidae,
Belemnocrinidae, Plicatocrinidae, Hyocrinidae (recent), Saccocomidae.

Order 2. _Adunata._--Monocyclica with dorsal cup primitively confined
to the patina and an occasional single anal; tegmen solid; portions of
the proximal brachials and their ambulacrals tend to be rigidly
incorporated in the theca. Arms fork once to thrice, and bear pinnules
on each or on every other brachial. BB fused to 3, 2 or 1.
(Eucladocrinus and Acrocrinidae offer peculiar exceptions to this
diagnosis.) Families: Platycrinidae, Hexacrinidae, Acrocrinidae.

Order 3. _Monocyclica Camerata._--Monocyclica in which the first, and
often the succeeding, orders of brachials are incorporated by
interbrachials in the dorsal cup, while the corresponding ambulacrals
are either incorporated in, or pressed below, the tegmen by
interambulacrals; all thecal plates united by suture, somewhat loose
in the earliest forms, but speedily becoming close, and producing a
rigid theca; mouth and tegminal food-grooves closed; arms pinnulate.

Sub-order i. _Melocrinoidea._--RR in contact all round; first
brachial usually quadrangular. Families: Glyptocrinidae,
Melocrinidae, Patelliocrinidae, Clonocrinidae, Eucalyptocrinidae,
Dolatocrinidae.

Sub-order ii. _Batocrinoidea._--RR separated by a heptagonal anal;
first brachial usually quadrangular. Families: Tanaocrinidae,
Xenocrinidae, Carpocrinidae, Barrandeocrinidae, Coelocrinidae,
Batocrinidae, Periechocrinidae.

Sub-order iii. _Actinocrinoidea._--RR separated by a hexagonal anal;
first brachial usually hexagonal. Families: Actinocrinidae,
Amphoracrinidae.

Sub-class II. _Dicyclica._--Crinoidea in which the base consists of BB
and IBB, the latter being liable to atrophy or fusion with the
proximale, but the aboral prolongations of the chambered organ are
always radial; new columnals may or may not be introduced at the
proximal end of the stem.

Order 1. _Dicyclica Inadunata._--Dicyclica in which the dorsal cup
primitively is confined to the patina and occasional intercalated
anals, and no other plates ever occur between RR (Grade: Distincta);
Br may be incorporated in the cup, with or without iBr, but never
rigidly, and their corresponding ambulacrals remain supra-tegminal
(Grade: Articulata); new columnals are introduced at the extreme
proximal end of the stem.

Sub-order i. _Cyathocrinoidea._--Tegmen stout with conspicuous
orals. Families: Carabocrinidae, Palaeocrinidae. Euspirocrinidae,
Sphaerocrinidae, Cyathocrinidae, Petalocrinidae, Crotalocrinidae,
Codiacrinidae, Cupressocrinidae, Gasterocomidae.

Sub-order ii. _Dendrocrinoidea._--Tegmen thin, flexible, with
inconspicuous orals. Families: Dendrocrinidae, Botryocrinidae,
Lophocrinidae, Scaphiocrinidae, Scytalecrinidae, Graphiocrinidae,
Cromyocrinidae, Encrinidae (preceding families are Distincta; the
rest Articulata), Pentacrinidae, including the recent _Isocrinus_
(fig. 14), Uintacrinidae, Marsupitidae, Bathycrinidae (recent).

Order 2. _Flexibilia._--Dicyclica in which proximal brachials are
incorporated in the dorsal cup, either by their own sides, or by
interbrachials, or by a finely plated skin, but never rigidly; plates
may occur between RR. Tegmen flexible, with distinct ambulacrals and
numerous small interambulacrals; mouth and food-grooves remain
supra-tegminal and open. Top columnal a persistent proximale, often
fusing with IBB, which are frequently atrophied in the adult.

All the Palaeozoic representatives have non-pinnulate arms, while the
Mesozoic and later forms have them pinnulate. There are other points
of difference, so that it is not certain whether the latter really
descended from the former. But assuming such a relationship we arrange
them in two grades.

Grade a. _Impinnata._--Families: Ichthyocrinidae, Sagenocrinidae,
and Taxocrinidae, perhaps capable of further division.

Grade b. _Pinnata._--Families: Apiocrinidae with the recent
_Calamocrinus_, Bourgueticrinidae with recent _Rhizocrinus_,
Antedonidae, Atelecrinidae, Actinometridae, Thaumatocrinidae (these
four recent families include free-moving forms with atrophied stem,
probably derived from different ancestors), Eugeniacrinidae,
Holopodidae (recent), Eudesicrinidae.

Order 3. _Dicyclica Camerata._--Dicyclica in which the first, and
usually the second, orders of brachials are incorporated in the dorsal
cup by interbrachials, at first loosely, but afterwards by close
suture. IBB always the primitive 5. An anal plate always rests on the
posterior basal; mouth and tegminal food-grooves closed; arms
pinnulate. Families: Reteocrinidae, Dimerocrinidae, Lampterocrinidae,
Rhodocrinidae, Cleiocrinidae.

Class IV. EDRIOASTEROIDEA.--Pelmatozoa in which the theca is composed
of an indefinite number of irregular plates, some of which are
variously differentiated in different genera; with no subvective
skeletal appendages, but with central mouth, from which there radiate
through the theca five unbranched ambulacra, composed of a double
series of alternating plates (covering-plates), sometimes supported by
an outer series of larger alternating plates (side-plates or
flooring-plates). In some forms at least, pores between (not through)
the ambulacral elements, or between them and the thecal plates, seem
to have permitted the passage of extensions from the perradial
water-vessels. Anus in posterior interradius, on oral surface, closed
by valvular pyramid. Hydropore (usually, if not always, present)
between mouth and anus. Families: Agelacrinidae, Cyathocystidae,
Edrioasteridae, Steganoblastidae. All Palaeozoic. The structure and
importance of _Edrioaster_ have been discussed above (figs. 11, 12).

Grade B. ELEUTHEROZOA--Echinoderma in which the theca, which may be
but slightly or not at all calcified, is not attached by any portion
of its surface, but is usually placed with the oral surface downwards
or in the direction of forward locomotion. Food is not conveyed by a
subvective system of ciliated grooves, but is taken in directly by the
mouth. The anus when present is typically aboral, and approaches the
mouth only in a few specialized forms. The aboral nervous system, if
indeed it be present at all, is very slightly developed. The
circumoesophageal water-ring may lose its connexion with the exterior
medium; the podia (absent only in some exceptional forms) may be
locomotor, respiratory or sensory in function, but usually are
locomotor tube-feet.

The classes of the Eleutherozoa probably arose independently from
different branches of the Pelmatozoan stem. The precise relation is
not clear, but the order in which they are here placed is believed to
be from the more primitive to the more specialized.

Class I. HOLOTHURIOIDEA.--Eleutherozoa normally elongate along the
oro-anal axis, which axis and the dorsal hydropore lie in the sagittal
plane of a secondary bilateral symmetry. The calcareous skeleton,
which may be entirely absent, is usually in the form of minute
spicules, sometimes of small irregular plates with no trace of a
calycinal or apical system; to these is added a ring of pieces
radiately arranged round the oesophagus. Ambulacral appendages take
the form of: (1) circumoral tentacles, (2) sucking-feet, (3) papillae;
of these (1) alone is always present. The gonads are not radiately
disposed.

The comparative anatomy of living forms, combined with the
evolutionary hypothesis sketched above, suggests that the early
holothurians possessed the following characters: subvective grooves
entirely closed; 5 radial canals, proceeding from the water-ring, gave
off branches furnished with ampullae to the podia on each side of
them, the 10 anterior podia being changed into cylindrical tentacles;
the transverse muscles of the body-wall formed a circular layer,
probably interrupted at the radii (though Ludwig believes the
contrary); longitudinal muscles as paired radial bands, without those
special retractors for withdrawing the anterior part of the body which
occur in many recent forms; a hydropore connected with the water-ring
by a canal in the dorsal mesentery; a gonopore behind the hydropore
connected by a single duct with a bunch of genital pouches on each
side of the mesentery; gut dextrally coiled, with a simple
blood-vascular system, and with an enlargement at the anus for
respiration, this eventually producing branched caeca called
"respiratory trees"; skeleton reduced to a ring of 5 radial and 5
interradial plates round the gullet, and small plates, with a
hexagonally meshed network, dispersed through the integument. Such a
form gave rise to descendants differing _inter se_ as regards the
suppression of the radial canals and of the podia, the form of the
tentacles, and the development of respiratory trees. These anatomical
facts are represented in the following classification by H. Ludwig:--

Order 1. _Actinopoda._--Radial canals supplying tentacles and podia.

A. With respiratory trees.
/Fam. 1, Holothuriidae.
(a) With podia < Fam. 4, Cucumariidae.
\Fam. 5, Molpadiidae.
(b) Without podia

B. Without respiratory trees.
(a) With podia Fam. 2, Elpidiidae.
(b) Without podia Fam. 3, Pelagothuriidae.

Order 2. _Paractinopoda._--Neither radial canals nor podia. Tentacles
supplied from circular canal. Fam. Synaptidae.

It is admitted, however, that this scheme does not represent the
probable descent or relationship of the families. Consideration of the
views of Ludwig himself, of H. Ostergren, and especially of R.
Perrier, suggests the following as a more natural if less obvious
arrangement.

Order 1. _Aspidochirota._--Tentacles more or less peltate; calcareous
ring when present simple and radially symmetrical; no retractors;
stone-canal often opens to exterior; genital tubes sometimes
restricted to left side in consequence of altered position of gut
(Fig. 15.) Families: Elpidiidae (deep-sea forms, with sub-famm.
Synallactinae, Deimatinae, Elpidiinae, Psychropotinae), Holothuriidae
(shallow water), Pelagothuriidae (pelagic).

Order 2. _Dendrochirota._--Tentacles simple or branched, never
peltate; calcareous ring well developed, often bilaterally
symmetrical; retractor muscles usually present; stone-canal opens
internally; genital tubes in right and left tufts.

Sub-order i. _Apoda._--No tube-feet or papillae, but tentacular
ampullae more or less developed. Mostly burrowers. Families:
Synaptidae (sub-famm. Synaptinae, Chirodotinae, Myriotrochinae),
Molpadiidae.

Sub-order ii. _Eupoda._--Tube-feet present, but tentacular ampullae
rudimentary or absent. Families: Cucumariidae (climbers and
crawlers), Rhopalodinidae (burrowers).

Class II. STELLIFORMIA (= ASTEROIDEA _sensu lato_).--Eleutherozoa with
a depressed stellate body composed of a central disk, whence radiate
five or more rays; this radiate symmetry affects all the systems of
organs, including the genital. The radial water-vessels lie in grooves
on the ventral side of flooring-plates (usually called "ambulacrals");
they and their podia are limited to the oral surface of the body and
their extremities are separated from the apical plates by a stretch
of dorsal integument containing skeletal elements; the opening of the
water-vascular system (madreporite) is not connected with a definite
apical plate or system of plates.

The starfish, brittle-stars and their allies (see STARFISH) have for
the last fifty years usually been divided into two classes--Asteroidea
and Ophiuroidea, each equivalent to the Holothurioidea or Echinoidea.
Recently, however, some authors, e.g. Gregory, have attempted to show
that these classes cannot be distinguished. It is true that some
specialized forms, such as the _Brisingidae_ among starfish,
_Astrophiura_ and _Ophioteresis_ among ophiurans, contravene the usual
diagnoses; but this neither obscures their systematic position, nor
does it alter the fact that since early Palaeozoic times these two
great groups of stellate echinoderms have evolved along separate
lines. If then we place these groups in a single class, it is not on
account of a few anomalous genera, but because the characters set
forth above sharply distinguish them from all other echinoderms, and
because we have good reason to believe that the ophiurans did not
arise independently but have descended from primitive starfish. For
that class Bell's name Stelliformia is selected since it avoids both
confusion and barbarism.

Sub-class I. _Asterida._--Stelliformia in which the ambulacral groove
always remains open and the podia serve as tube-feet (fig. 12, B); the
rays as a rule pass gradually into the disk, and contain both genital
glands and caecal extensions of the digestive system; an anus usually
present; respiration is by tubular extensions from the body-cavity
(papulae); skeletal appendages, in addition to small spines, are
either small grasping organs (pedicellariae), or clumped spines
(paxillae), or branched spines bearing a membrane.

No existing classification of the Asterida is satisfactory even for
the recent forms, still less when the older fossils are considered. A
separation of the latter as Palasterida, because of their alternating
ambulacrals, from the recent Euasterida with opposite ambulacrals, is
now discarded and an attempt made to arrange the Palasterida in
divisions originally established for Euasterida. Those divisions fall
under three schemes. C. Viguier has divided the starfish into:
_Asteries ambulacraires_, with plates of ambulacral origin prominent
in the mouth-skeleton, pedicellariae stalked, and straight or crossed,
podial pores usually quadriserial; _Asteries adambulacraires_, with
adambulacrals prominent in the mouth-skeleton, pedicellariae sessile,
and forcipiform or valvular, podial pores usually biserial. Perrier,
at first laying greater stress on the nature of the pedicellariae and
afterwards on the form of the mouth-skeleton, has gradually perfected
a scheme of five orders: (1) _Forcipulata_, with pedicellariae
stalked, and straight or crossed; (2) _Spinulosa_, with pedicellariae
sessile and forcipiform; (3) _Velata_, with membraniferous spines; (4)
_Paxillosa_, pedicellariae represented by an ossicle of the test and
the spines covering it, the whole forming a paxilla; (5) _Valvata_ or
_Granulosa_, with pedicellariae sessile and valvular or salt-cellar
shaped. A more widely accepted scheme is that of W.P. Sladen, who
divided the Euasterida into two orders; (1) _Phanerozonia_, with
marginals large and highly developed, the supero-marginals and
infero-marginals contiguous, with papulae confined to the dorsal
surface, with ambulacrals well spaced and usually broad, adambulacrals
prominent in the mouth-skeleton, with pedicellariae sessile; (2)
_Cryptozonia_, with marginals inconspicuous and somewhat atrophied in
the adult, the supero-marginals separated from the infero-marginals by
intercalated plates, with papulae distributed over the whole body,
with ambulacrals crowded and narrow, either ambulacrals or
adambulacrals prominent in the mouth-skeleton, with pedicellariae
stalked or sessile.

We give here a list of the families separated into Sladen's orders and
grouped under Perrier's divisions, extinct families being marked [+].

a, Ambulacral plates.
b, Adambulacral plates.
c and d, Inferior and superior lateral plates.
e, Dorsal plates with paxillae. Certain supra-ambulacral plates,
which also exist, are not shown.]

1. _Phanerozonia._--_Unclassed Famm._, [+] Palaeasteridae, [+]
Palasterinidae, [+] Taeniasteridae, [+] Aspidosomatidae. _Paxillosa_,
Luidiidae, Astropectinidae (fig. 16), Archasteridae restr. Verrill,
Porcellanasteridae, Chaetasteridae. _Valvata_, Benthopectinidae,
Goniopectinidae, Plutonasteridae, Odontasteridae, Pentagonasteridae,
Antheneidae, Pentacerotidae, Gymnasteriidae. _Spinulosa_, Poraniidae,
Asterinidae.

2. _Cryptozonia._--_Unclassed Famm._, [+] Sturtzasteridae (=
Palaeocomidae Greg.), [+] Lepidasteridae, [+] Tropidasteridae.
_Valvata_, Linckiidae restr. Perr. _Spinulosa_, Echinasteridae,
Solasteridae (fig. 17), Korethrasteridae. _Velata_, [+]
Palasteriscidae, Pterasteridae, Pythonasteridae, Myxasteridae.
_Forcipulata_, Stichasteridae, Zoroasteridae (fig. 3, D),
Heliasteridae, Pedicellasteridae, Asteriidae, Brisingidae.

Sub-class II. _Ophiurida._--Stelliformia in which the ambulacral
groove, though open in the oldest forms, soon becomes closed, while
the podia cease to serve as tube-feet; the rays as a rule spring
abruptly from the disk and contain neither genital glands nor
digestive caeca; no anus; respiration may be through clefts at the
bases of the rays, but not by papulae; skeletal appendages confined to
spines, usually of simple structure.

There is as yet no satisfactory classification of the Ophiurida into
orders expressing lines of descent; even as regards families, leading
writers are at variance. The following scheme is based on the attempts
of E. Haeckel, F.J. Bell, J.W. Gregory, B. Sturtz, J.O.E. Perrier, and
A.E. Verrill. Extinct families marked [+].

Grade A. _Palophiurae._--Ambulacrals not yet forming complete
vertebrae; plates of disk not yet specialized into mouth, radial or
genital shields.

Stage a. _Allostichia_ (= Lysophiurae).--Ambulacrals alternating and
unfused, groove uncovered by ventral arm-plates. Families: [+]
Protasteridae, [+] Protophiuridae.

Stage b. _Zygostichia._--Ambulacrals opposite and, except in
Ophiurinidae, fused; ventral arm-plates developed in some. Families:
[+] Ophiurinidae, [+] Lapworthuridae, [+] Furcasteridae, [+]
Palastropectinidae, [+] Eoluididae, [+] Palaeophiomyxidae.

Grade B. _Colophiurae._--Ambulacral pairs fused to form vertebrae with
definite articular surfaces; mouth, radial and genital shields
developed, though not all need be present in any one form.

Order 1. _Streptophiurae._--Rays simple and capable of coiling, since
the vertebrae articulate by a ball-and-socket joint; arm-plates
incompletely developed. Families: [+] Onychasteridae, Ophiohelidae,
Ophioscolecidae, Ophiomyxidae, Hemieuryalidae, Astrophiuridae;
unclassified genera, e.g. _Ophioteresis_, _Ophiosciasma_,
_Ophiogeron_.

Order 2. _Zygophiurae._--Rays simple and prevented from coiling by
processes on the vertebral joints (fig. 18); dorsal, ventral and
lateral arm-plates present.

A, Proximal joint-face.
B, Distal joint-face.
c, Ventral groove, where lies the water-vessel, from which branches
pass through the ossicle, emerging as podia at e and e.]

Sub-order i. _Brachyophiurae._--Spines short, simple, pointing
towards the end of the arm. Families: Pectinuridae (=
Ophiodermatidae), Ophiolepididae.

Sub-order ii. _Nectophiurae._--Spines may be variously elaborated
and are set more at right angles to the arm-axis. Families:
Amphiuridae, Ophiacanthidae, Ophiocomidae, Ophiothrichidae.

Order 3. _Cladophiurae_ (= Euryalae). Rays simple or branched, capable
of coiling, since the vertebrae articulate by surfaces of hour-glass
shape; ventral arm-plates, and often the others, much reduced; spines
reduced or absent. Families: Euryalidae, Gorgonocephalidae,
Astrochelidae, Astroschemidae, Astronycidae.

The Silurian genera _Eucladia_ and _Euthemon_ have the rays greatly
reduced and merged in the disk, so that the ambulacrals are unseen.
There are a few large dorsal, lateral and ventral arm-plates, and at
the angles of the latter emerge huge podia with a granular or plated
skin. There are five prominent mouth-shields and a separate
madreporite on the ventral surface. These genera attained the
Colophiuran grade in respect of external plating, but it is unlikely
that they or their ancestors had acquired even the Streptophiuran
type of vertebra. Sollas has separated them as an order _Ophiocistia_.

Class III. ECHINOIDEA.--Eleutherozoa with a test of roughly circular,
subpentagonal or elliptical outline, spheroidal, domed or flattened,
of primary pentameric symmetry affecting all systems of organs except
the gut. The radial water-vessels lie within the test through which
their podia pass (fig. 12, D); the ambulacra thus formed are
continuous from the peristome to the apical system of plates; the
hydropore is connected with a definite plate of that system, and thus
marks a secondary bilateral symmetry. An anus is present either within
the apical system (endocyclic, fig. 3, A and B), or outside it in an
interradius (exocyclic, fig. 19, 7), thus initiating yet another
bilateral symmetry. Skeletal appendages are spines (radioles),
pedicellariae, and, in some forms, minute sense-organs called
sphaeridia.

The echinoids or sea-archins (see SEA-URCHIN) may be grouped under the
following orders, here named in the sequence of their appearance in
the rocks.

Order 1. _Bothriocidaroida._--Ambulacrals simple, each with two pores
vertically superposed, 2 columns to each ambulacrum; interambulacrals
multi-tuberculate, in 1 column, none passing on to or resorbed by the
peristome; mouth central, jaws unknown, no external gills or
sphaeridia; anus aboral, endocyclic. Sole genus _Bothriocidaris_ (fig.
5), Ordovician.

Order 2. _Melonitoida._--Ambulacrals simple, each with two pores
horizontally juxtaposed, in 2 to 18 columns; interambulacrals
granulate with occasional tubercles, in 3 to 11 columns, not more than
one row passing on to the peristome; mouth central, with jaws, no
external gills or sphaeridia; anus aboral, endocyclic. Families:
Palechinidae (fig. 19, 1), Melonitidae and Lepidesthidae, Silurian to
Carboniferous.

Order 3. _Cystocidaroida._--Ambulacrals simple, each with one or two
pores, which sometimes pass between rather than through the plates, in
2 columns; interambulacrals, uni- or multi-tuberculate, in numerous
(say 10 or more) columns, none passing on to peristome; mouth central
with jaws, no external gills or sphaeridia; position of anus doubtful,
acyclic, i.e. no apical system so far as known. Include only
_Echinocystis_, _Palaeodiscus_ and (?) _Myriastiches_, all Upper
Silurian.

Order 4. _Cidaroida._--Ambulacrals simple, each with two pores
horizontally juxtaposed, in 2 columns; interambulacrals
unituberculate, in 2 to 11 columns, some rows may pass on to the
peristome; mouth central, with jaws, no external gills or sphaeridia;
anus aboral, endocyclic. Families: Lepidocentridae and
Archaeocidaridae (fig. 19, 2), Devonian and Carboniferous; Cidaridae
(fig. 19, 3, 4). Permian to present; Diplocidaridae and Tiarechinidae,
Mesozoic.

Order 5. _Diademoida._--Ambulacrals generally compound, with two pores
obliquely juxtaposed, in 2 columns as in all subsequent orders;
interambulacrals usually with large radioles surrounded by smaller
ones, as in Cidaroida, in 2 columns as in all subsequent orders, only
one plate resorbed; mouth central, with jaws and external gills,
sphaeridia present; anus aboral endocyclic. J.W. Gregory divides this
into four suborders, each representing a distinct evolutionary series;
i. _Calycina_, Saleniidae (fig. 19, 5) and Acrosaleniidae; ii.
_Arbacina_, Hemicidaridae and Arbaciidae; iii. _Diademina_,
Orthopsidae, Diadematidae, Diplopodiidae, Pedinidae, Cyphosomatidae,
and Echinothuridae; iv. _Echinina_, Temnopleuridae, Triplechinidae,
Strongylocentrotidae and Echinometridae. The order is Triassic to
Recent.

1, _Palaeechinus_; Carboniferous.
2, A plate and radiole of _Archaeocidaris_; Carboniferous.
3, A radiole of _Cidaris_; Jurassic.
4, _Hemicidaris_; Mid. Jurassic.
5, _Salenia_; Cretaceous.
6, _Dysaster_; Jurassic.
7, _Enallaster_: Cretaceous.
8, _Catopygus_; Cretaceous.]

Order 6. _Holectypoida._--Ambulacrals sometimes compound, with one or
two pores to a plate, some dorsal podia begin to assume respiratory
function; interambulacrals multi-tuberculate, none resorbed; mouth
central, with jaws weak or wanting, with external gills and
sphaeridia; anus exocyclic. Families: Pygasteridae, Discoidiidae,
Galeritidae, Conoclypeidae; Jurassic to Recent.

Order 7. _Spatangoida._--Ambulacrals simple, with two pores
juxtaposed, dorsal podia respiratory; interambulacrals bearing
numerous small spines, none resorbed; mouth central or shifted
forwards, with no jaws or external gills, sphaeridia numerous; anus
exocyclic. As the mouth moves forward and the anus downward, the
posterior interambulacrals between them are enlarged and strengthened
so as to form a sternum. The order may therefore be divided into: (i.)
_Asternata_, Famm. Echinoneidae, Nucleolitidae and Cassidulidae (fig.
19, 8); (ii.) _Sternata_, Famm. Collyritidae (fig. 19, 6),
Echinocorytidae, Spatangidae (fig. 19, 7), Palaeostomidae, and
Pourtalesiidae; Jurassic to Recent.

Order 8. _Clypeastroida._--Ambulacrals simple or compound, with two
pores juxtaposed, dorsal podia respiratory; interambulacrals
multi-tuberculate, none resorbed; mouth central with flattened unequal
jaws, reduced external gills, and few sphaeridia; anus exocyclic.
Families: Fibulariidae, Laganidae, Scutellidae, Clypeastridae;
Cretaceous to Recent.
_
Cambrian |
|
|
Ordovician BOTHRIOCIDAROIDA (jaws unknown) |
/ \ |
/ \ columns
Silurian MELONITOIDEA \ unfixed
# CYSTO- \ in
## CIDAR- \ number
### OIDA \ |
Devonian ### CIDAROIDA |
### # |
### # |
Carboniferous ### ##\ _|
## ## \
## ## \ _
Permian # ## \ |
## \ |
Trias ## DIADEMOIDA columns
## # \ 20
Jurassic ## ## \ HOLECTYPOIDA |
## ### / # \ SPATANGOIDEA |
Cretacious ## ### CLYPEASTROIDEA # \ # |
## ### # ## ## |
Tertiary ## ### ## ## ### |
## ### ### # ### |
Recent ## ### ### # #### _|

|----------jaws lofty--------| jaws flat-reduced ---- lost

|------abranchiate-----| |-----branchiate-----| |-lipobranchiate-|

|----no sphaeridia-----| |--------------sphaeridia---------------|

|-------endocyclic---------| |------------exocyclic--------------|

The probable relationship of these orders is shown in the annexed
table. Here the Cystocidaroida occupy an isolated position. It is,
however, quite possible that _Echinocystis_ may some day be referred
to the Cidaroida, and _Palaeodiscus_ to the Melonitoida. This would
leave the Echinoid scheme remarkably simple, with the Melonitoida and
Cidaroida as divergent branches from an ancestor like
_Bothriocidaris_; but while the former branch soon decayed, the latter
continues to flourish at the present day. To take the Echinoidea now
living, and to divide them into Endocyclica and Exocyclica, Branchiate
and Abranchiate, Gnathostomata and Atelostomata, is easy and
convenient; or again to distinguish as Palechinoidea those
pre-Jurassic genera which do not conform to the fixed type of twenty
vertical columns found in the later Euechinoidea, is to express an
interesting fact; but all such divisions obscure the true
relationships, and the corresponding terms should be recognized as
descriptive rather than classificatory.

AUTHORITIES.--In addition to the works referred to at the beginning of
the article, the following deal with the general subject: Bather,
Gregory and Goodrich, "Echinoderma," in Lankester's _Treatise on
Zoology_ (London, 1900); F.J. Bell, _Catalogue of the British
Echinoderms in the British Museum_ (London, 1892); P.H. Carpenter,
"Notes on Echinoderm Morphology," _Quart. Journ. Micr. Sci._,
1878-1887; Y. Delage and E. Herouard, _Traite de zoologie concrete,
iii., Echinodermes_ (Paris, 1904); A. Lang, _Text-Book of Comparative
Anatomy_, transl., part ii. (London, 1896); Ludwig and Hamann,
"Echinodermen," in Bronn's _Klassen und Ordnungen des Tierreichs_
(Leipzig, 1889), in progress; M. Neumayr, _Die Stamme des Tierreiches_
(Wien, 1889); P.B. and C.F. Sarasin, "Uber die Anatomie der
Echinothuriden und die Phylogenie der Echinodermen," _Ergebnisse
naturw. Forsch. auf Ceylon_, Bd. i Heft 3 (Wiesbaden, 1888); R. Semon,
"Die Homologien innerhalb des Echinodermenstammes," _Morph. Jahrb._
(1889); W.P. Sladen, "Homologies of the Primary Larval Plates in the
Test of Brachiate Echinoderms," _Quart. Journ. Micr. Sci._, 1884; K.A.
v. Zittel, _Handbuch der ... Palaozoologie_, i. pp. 308-560 (Munchen,
1879); also Grundzuge, translated and revised by C.R. Eastman as
_Text-Book of Palaeontology_ (New York and London, 1899). The larger
treatises here mentioned contain very full bibliographies, and a
complete analytical index to the annual literature of the Echinoderma
has for many years been published in the _Zoological Record_ (London).
(F. A. B.)

FOOTNOTE:

[1] Sometimes called "Echinodermata," a Greek name meaning
"sea-urchin-skins," which was invented by J.T. Klein (1734) to denote
the tests of the Echini or sea-urchins; its later use for the animals
themselves, or for the whole phylum, was an error in both history and
etymology.

ECHINUS (Gr. for "hedge-hog" or "sea-urchin"), in architecture, the convex moulding which supports the abacus of the Doric column. The term is sometimes given to the _ovolo_ of the Ionic capital, especially when curved with the egg-and-tongue enrichment. The origin of this use of the word in architecture, which comes down from ancient times, is uncertain.

ECHIUROIDEA (Gr. [Greek: echis], adder, and [Greek: oura], tail), the zoological name for a small group of marine animals which show in their larval life-history a certain degree of segmentation, and are therefore grouped by some authorities as Annelids. Formerly, together with the Sipunculoidea and Priapuloidea, they made up the class Gephyrea, but on the ground that they retain in the adult a large preoral lobe (the proboscis), that they have anal vesicles, that their anus is terminal, that setae are found, and finally that they are segmented in the larval stage, they have been removed from the class, which by the proposed further separation of the Priapuloidea on account of their unique renal and reproductive organs, has practically ceased to exist.

; B, B. _fuliginosa_. Both natural size. a, grooved proboscis; b, mouth; c, ventral hooks; d, anus.]

Echiuroids are animals of moderate size, varying roughly from one to six or seven centimetres in length, exclusive of the proboscis. This organ is capable of very considerable extension, and may attain a length in _Bonellia viridis_ of about a metre and a half (fig. 1). It is grooved ventrally and ciliated. At its attachment to the body the groove sinks into the mouth. In _Bonellia_ the proboscis is forked at its free end, but in the other genera it is short and unforked. The body is somewhat sausage-shaped, with the anus at the posterior extremity, surrounded in _Echiurus_ by a single or double ring of setae. The skin is usually wrinkled, and in _B. viridis_, _Thalassema lankesteri_, _Th. baronii_, _Hamingia arctica_, and in the larva of many species, is of a lively green colour. A pair of curved bristles, formed in true setal sacs as in Chaetopoda, project from the body a short distance behind the mouth, and are moved by special muscles; they are of use in helping the animal to move slowly about, and they take a large share in the burrowing movements (C.B. Wilson, _Biol. Bull._, 1900), for some species tunnel in the mud and sand and form more or less permanent burrows, the walls of which are strengthened by mucus secreted from the skin. The openings of the burrows become silted up, leaving, however, a small aperture through which the proboscis is extruded. This organ carefully searches the neighbourhood for particles of food. When these are found the grooved proboscis folds its walls inwards, and the cilia pass the particles down the tube thus formed to the mouth. Echiuroids also move by extending the proboscis, which takes hold of some fixed object, and, then contracting, draws the body forwards. Recently it has been shown that _Echiurus_ swims freely at night-time, using for locomotion both the proboscis and the contraction of the muscles of its body-wall. The motion is described as "gyratory," and the anterior end is always carried foremost. Those species which do not burrow usually conceal themselves in crevices of the rocks or under stones, or at times in empty Mollusc or Echinid shells. They are occasionally used by fishermen for bait.

a, Proboscis cut short.
b, Bristle passing through the mouth into the pharynx.
c, Coiled intestine.
d, Anal tufts or vesicles.
e, Ventral nerve cord.
f, Ovary borne on ventral vessel running parallel with e.
g, Position of anus.
h, Position of external opening of nephridium.
i, Nephridium--the line points towards, but does not reach, the
internal opening.]

_Anatomy_ (fig. 2).--A thin cuticle covers the epidermis, which
contains mucus-secreting glands. Beneath the epidermis is a layer of
circular muscles, then a layer of longitudinal, and finally in some
cases a layer of oblique muscle-fibres. The inner face of this
muscular skin is lined by a layer of epithelium. The coelomic
body-cavity is spacious. It does not extend into the proboscis, which
is a solid organ traversed by the nervous and vascular rings, but
otherwise largely built up of muscle fibres and connective tissue.
Many sense-cells lie in the epidermis. The ciliated ventral groove of
the proboscis leads at its base into the simple mouth, which gives
access to the thin-walled alimentary canal. This is longer than the
body, and to tuck it away it is looped from side to side. The loops
are supported by strands of connective tissue, which in some species
are united so as to form a dorsal mesentery, whilst traces of a
ventral mesentery are met with anteriorly and posteriorly (H.L.
Jameson, _Zool. Jahrb. Anat._, 1899). The alimentary canal is
divisible into fore-gut, mid-gut and hind-gut, and the first-named can
be further divided into pharynx, oesophagus, gizzard and crop, mainly
on histological grounds. The mid-gut is characterized by the presence
of a ciliated groove, from which arises the collateral intestine or
siphon, a second tube which rejoins the alimentary canal lower down.
Similar collateral intestines are familiar in the Echinids and certain
Polychaets (Capitellidae). The rectum receives the openings of a pair
of very characteristic organs, the anal vesicles. Each consists of a
branching tube, the tips of whose twigs terminate in minute ciliated
funnels. The anal vesicles are thought to be excretory; whether this
be so or not, they undoubtedly have some influence on the amount of
fluid found in the coelom. The coelomic fluid contains as a rule both
amoeboid and rounded corpuscles, and, when ripe, the products of the
gonads. A closed system of vessels, usually called the vascular
system, is present. There are, however, no capillaries connected with
this, and it is confined to certain portions of the body. It can
possess few of the functions usually associated with a vascular
system, and its main use is probably to assist in the expansion of the
proboscis. The system consists of the following parts:--A dorsal
vessel applied to the alimentary canal is continued anteriorly into a
median vessel, which traverses the proboscis to its tip. Here the
vessel splits, and each half returns along the lateral edge of the
proboscis; they reunite around the oesophagus and form a single
ventral vessel, which lies above the ventral nerve-cord. The ventral
vessel, which ends solidly behind, sends off a branch which forms a
ring around the intestine and opens into the posterior extremity of
the dorsal vessel. In _Echiurus_ and _Thalassema_ the same vessel
forms a ring round a stout muscle, which connects the bases of the two
ventral setae before passing to surround the intestine. Amoeboid
corpuscles float in the fluid contents. The nephridia vary in number
from a single one in _Bonellia_ to three pairs in many species of
_Thalassema_. Their external openings are ventral, and on the same
level as the ciliated funnel-shaped nephrostomes. The posterior wall
of the organ is produced into a long blind sac, which is lined by
secretory cells. The nervous system is a single ventral cord, which
starts from a circumoesophageal ring. This ring is involved in the
growth of the proboscis, and is drawn out with it. Thus there is a
lateral nerve near each edge of the proboscis which unites with its
fellow dorsally above the oesophagus at the tip of the proboscis, and
ventrally beneath the oesophagus, where they fuse to form the ventral
nerve-cord. There are no specialized ganglia, but ganglion-cells are
scattered uniformly along the nerve-cords. The ventral cord gives off
rings, which run into the skin at regular intervals. The reproductive
cells are modified coelomic cells, which lie on the ventral vessel.
They escape into the coelomic fluid and there develop. When mature
they leave the body through the nephridia. _Bonellia_ and _Hamingia_
are very interesting examples of sexual dimorphism. The female has the
normal Echiuroid structure, but the male is reduced to a minute,
flattened, planarian-like organism, which passes its life usually in
the company of two or three others in a special recess of the
nephridia of the female. Its structure may be gathered by a reference
to fig. 3.

a, Generative pore with spermatozoa coming out.
b, Anterior blind end of intestine attached to the parenchymatous
tissue by muscular strands.
c, Green wandering cells containing chlorophyll.
d, Parenchymatous connective tissue.
e, Epidermis.
i, Intestine.
j, Vas deferens.
l, Internal opening of vas deferens.
m, The left anal vesicle.
n, Spermatozoa in the body-cavity.]

_Larva._--The larva is a typical trochosphere, which, although of a
temporary character, shows a distinct segmentation of the mesoblast,
of the nervous system, and of the ciliated and pigmented structures in
the skin, resembling that of Chaetopods. The preoral lobe persists as
the proboscis. The sexes of the larvae are not determinable in the
early stages, but when a certain growth has been reached in Bonellia
the males seek the proboscis of the adult females, and passing into
the mouth undergo there the transformation into the planarian-like
parasite which is the fully-formed male. This now creeps along the
body of the female and takes up its home in her nephridia.

_Classification and Distribution._--The Echiuroidea consists of the following genera:--(1) _Bonellia_ (Rol.), with four species, widely distributed, but inhabiting the temperate and warmer waters of each hemisphere. (2) _Echiurus_ (Guerin-Meneville), with four species. This genus reaches from the Arctic waters of both hemispheres into the cooler temperate regions. (3) _Hamingia_ (Kor. and Dan.), with one species, which has been taken in the Arctic Sea and the Hardanger Fjord. (4) _Saccosoma_ (Kor. and Dan.) was described from a single specimen dredged about half-way between Iceland and Norway. (5) _Thalassema_ (Gaertner, Lamarck), with twenty-one species. This genus is in the main a denizen of the warmer waters of the globe. Sixteen species are found only in tropical or subtropical seas, three species are Mediterranean (_Mt. Stat. Neapel_, 1899), whilst three species are from the eastern Atlantic, where the temperature is modified by the Gulf Stream (Shipley; see Willey's _Zoological Results_, part iii. 1899; _Proc. Zool. Soc. Lond._, 1898, 1899; and _Cambridge Natural History_, ii.). The following are found in the British area:--_E. pallasii_ (Guerin-Meneville), _Th. neptuni_ (Gaertner), and _Th. lankesteri_ (Herdman, _Q.J.M.S._, 1898).

_Affinities._--The occurrence of trochosphere larva and the temporary segmentation of the body have led to the belief that the Echiuroids are more nearly allied to the Annelids than to any other phylum. This view is strengthened by certain anatomical and histological resemblances to the genus _Sternaspis_, which in one species, _S. spinosa_, is said to carry a bifid proboscis resembling that of the Echiuroids. (A. E. S.)

ECHMIADZIN, or ITSMIADSIN, a monastery of Russian Transcaucasia, in the government of Erivan, the seat of the Catholicus or primate of the Armenian church. It is situated close to the village of Vagarshapat, in the plain of the Aras, 2840 ft. above the sea, 12 m. W. of Erivan and 40 N. of Mount Ararat. The monastery comprises a pretty extensive complex of buildings, and is surrounded by brick walls 30 ft. high, which with their loopholes and towers present the appearance of a fortress. Its architectural character has been considerably impaired by additions and alterations in modern Russian style. On the western side of the quadrangle is the residence of the primate, on the south the refectory (1730-1735), on the east the lodgings for the monks, and on the north the cells. The cathedral is a small but fine cruciform building with a Byzantine cupola at the intersection. Its foundation is ascribed to St Gregory the Illuminator in 302. Of special interest is the porch, built of red porphyry, and profusely adorned with sculptured designs somewhat of a Gothic character. The interior is decorated with Persian frescoes of flowers, birds and scroll-work. It is here that the Catholicus confers episcopal consecration by the sacred hand (relic) of St Gregory; and here every seven years he prepares with great solemnity the holy oil which is to be used throughout the churches of the Armenian communion. Outside of the main entrance are the alabaster tombs of the primates Alexander I. (1714), Alexander II. (1755), Daniel (1806) and Narses (1857), and a white marble monument, erected by the English East India Company to mark the resting-place of Sir John Macdonald Kinneir, who died at Tabriz in 1830, while on an embassy to the Persian court. The library of the monastery is a rich storehouse of Armenian literature (see Brosset's _Catalogue de la bibliotheque d'Etchmiadzin_, St Petersburg, 1840). Among the more remarkable manuscripts are a copy of the gospels dating from the 10th or 11th century, and three bibles of the 13th century. A type-foundry, a printing-press and a bookbinding establishment are maintained by the monks who supply religious and educational works for their co-religionists.

To the east of the monastery is a modern college and seminary. Half a mile to the east stand the churches of St Ripsime and St Gaiana, two of the early martyrs of Armenian Christianity; the latter is the burial-place of those primates who are not deemed worthy of interment beside the cathedral. From a distance the three churches form a fairly striking group, and accordingly the Turkish name for Echmiadzin is Uch-Kilissi, or the Three Churches. The town of Vagarshapat dates from the 6th century B.C.; it takes its name from King Vagarsh (Vologaeses), who in the 2nd century A.D. chose it as his residence and surrounded it with walls. Here the apostle of Armenia, St Gregory the Illuminator, erected a church in 309 and with it the primacy was associated. In 344 Vagarshapat ceased to be the Armenian capital, and in the 5th century the patriarchal seat was removed to Dvin, and then to Ani. The monastery was founded by Narses II., who ruled 524-533; and a restoration was effected in 618. The present name of the monastery was adopted instead of Vagarshapat in the 10th century. At length in 1441 the primate George brought back the see to the original site. (P. A. K.; J. T. Be.)

ECHO (Gr. [Greek: echo]), in Greek mythology, one of the Oreades or mountain nymphs, the personification of the acoustical phenomenon known by this name. She was beloved by Pan, but rejected his advances. Thereupon the angry god drove the shepherds of the district mad; they tore Echo in pieces, and scattered her limbs broadcast, which still retained the gift of song (Longus iii. 23). According to Ovid (_Metam._ iii. 356-401), Echo by her incessant talking having prevented Juno from surprising Jupiter with the Nymphs, Juno changed her into an "echo"--a being who could not speak till she was spoken to, and then could only repeat the last words of the speaker. While in this condition she fell in love with Narcissus, and in grief at her unrequited affection wasted away until nothing remained but her voice and bones, which were changed into rocks. The legends of Echo are of late, probably Alexandrian, origin, and she is first personified in Euripides.

In acoustics an "echo" is a return of sound from a reflecting surface (see SOUND: _Reflection_).

See F. Wieseler, _Die Nymphe Echo_ (1854), and _Narkissos_ (1856); P.
Decharme in Daremberg and Saglio's _Dictionnaire des antiquites_.

ECHTERNACH, a town in the grand duchy of Luxemburg, on the Sure, close to the Prussian frontier. Pop. (1905) 3484. It is the oldest town in Luxemburg, and was the centre from which the English Saint Willibrord converted the people to Christianity in the 7th century. There are the Benedictine abbey, the hospital almshouse, which is said to be the oldest hospital in Europe except the Hotel-Dieu in Paris, and the church of St Peter and St Paul. The Benedictine abbey has been greatly shorn of its original dimensions, but the basilica remains a fair monument of Romano-Gothic art. The church of St Peter and St Paul stands on an isolated mound, and for the ascent sixty steps have been built in the side, and these are well worn by the tread of numerous pilgrims who come in each succeeding year. The interior of the church is curious more than imposing, and is specially noteworthy only for its gloom. Under the altar, and below a white marble effigy of himself, lies Saint Willibrord.

Echternach is famous, however, in particular for the dancing procession held on Whit-Tuesday every year. The origin of this festival is uncertain, but it dates at least from the 13th century and was probably instituted during an outbreak of cholera. Nowadays it is an occasion of pilgrimage, among Germans and Belgians as well as Luxemburgers, for all sick persons, but especially for the epileptic and those suffering from St Vitus' dance. The ceremony is interesting, and the Roman Catholic Church lends all its ritual to make it more imposing. The archbishop of Trier attends to represent Germany, and the bishop of Luxemburg figures for the grand duchy. There is a religious ceremony on the Prussian side of the bridge over the Sure, and when it is over the congregation cross into the duchy to join the procession, partly religious, partly popular, through the streets of the town. The religious procession, carrying cross and banners and attended by three hundred singers, comes first, chanting St Willibrord's hymn. Next comes a band of miscellaneous instruments playing as a rule the old German air "Adam had seven sons," and then follow the dancers. Many of these are young and full of life and health and dance for amusement, but many others are old or feeble and dance in the hope of recovery or of escaping from some trouble, but on all alike the conditions of the dance are incumbent. There are three steps forward and two back; five steps are thus taken to make one in advance. This becomes especially trying at the flight of steps mounting to the little church where the procession ends in front of the shrine of the great saint. There are sixty steps, but it takes three hundred to reach the top for the final time. It is said that those who fall from age or weariness have to be dragged out of the way by onlookers or they would be trampled to death by the succeeding waves of dancers. The procession, although it covers a distance of less than a mile, is said to take as much as five hours in its accomplishment. In olden days the abbey was the goal of the procession, and King William I. of the Netherlands--great-grandfather of Queen Wilhelmina--changed the day from Tuesday to Sunday so that a working day should not be lost. This reform did not answer, and the ancient order was restored. Some critics see in the dancing procession of Echternach merely the survival of the spring dance of the heathen races, but at any rate it invests the little town with an interest and importance that would otherwise be lacking.

ECHUCA, a borough of the county of Rodney, Victoria, Australia, 156 m. by rail N. of Melbourne. Pop. (1901) 4075. It is situated on the river Murray, across which it is connected by bridge with Moama, on the New South Wales side, whence a railway runs to Deniliquin. The town is the terminus of the Murray River railway and the entrepot of the overland intercolonial trade; it has large wool stores, saw-mills, coach factories, breweries and soap-works. The rich agricultural district is noted for its vineyards.

ECIJA, a town of southern Spain, in the province of Seville; on the Cadiz-Cordova railway and the left bank of the river Genil. Pop. (1900) 24,372. The river, thus far navigable, is here crossed by a fine old bridge; and the antiquity of the town betrays itself by the irregularity of its arrangement, by its walls and gateways, and by its numerous inscriptions and other relics. Its chief buildings include no fewer than twenty convents, mostly secularized. The principal square is surrounded with pillared porticoes, and has a fountain in the centre; and along the river bank there runs a fine promenade, planted with poplar trees and adorned with statues. From an early period the shoemakers of Ecija have been in high repute throughout Spain; woollen cloth, flannel, linen and silks are also manufactured. The vicinity is fertile in corn and wine, and cotton is cultivated. The heat is so great that the spot has acquired the sobriquet of _El Sarten_, or the "Frying-pan" of Andalusia. Ecija, called _Estija_ by the Arabs, is the ancient _Astigis_, which was raised to the rank of a Roman colony with the title of _Augusta Firma_. According to Pliny and Pomponius Mela, who both wrote in the 1st century A.D., it was the rival of Cordova and Seville. If local tradition may be believed, it was visited by the apostle Paul, who converted his hostess Santa Xantippa; and, according to one version of his life, it was the see of the famous St Crispin (q.v.) in the 3rd century.