See also:

• ECHIUROIDEA (Gr: 'xis, adder, and ovpa, tail)

ECHIUROIDEA (Gr: 'xis, See also:

• ADDER

adder, and ovpa, tail)  , the zoo-logical name for a small See also:

• GROUP

group of marine animals which show in their larval See also:

• LIFE

life-See also:

• HISTORY

history a certain degree of segmentation, and are therefore grouped by some authorities as Annelids . Formerly, together with the See also:

• SIPUNCULOIDEA

Sipunculoidea and See also:

• PRIAPULOIDEA

Priapuloidea, they made up the class See also:

• GEPHYREA

Gephyrea, but on the ground that they retain in the adult a large preoral See also:

• LOBE

lobe (the See also:

• PROBOSCIS

proboscis), that they have anal vesicles, that their anus is terminal, that setae are found, and finally that they are segmented in the larval See also:

• STAGE (Fr. 6/age; from Lat. stare, to stand)

stage, they have been removed from the class, which by the proposed further separation of the Priapuloidea on See also:

• ACCOUNT
• ACCOUNT (through O. Fr. acont, Late Lat. comptum, cornputare, to calculate)

account of their unique renal and reproductive See also:

• ORGANS

organs, has practically ceased to exist . Echiuroids are animals of moderate See also:

• SIZE

size, varying roughly from one to six or seven centimetres in length, exclusive of the proboscis . This See also:

• ORGAN

organ is capable of very considerable ex-tension, and may attain a length in Bonellia viridis of about a See also:

• METRE ((terpuc?, sc. rFxvf, from Gr. Or poi', measure)

metre and a See also:

• HALF

half (fig . 1) . It is grooved ventrally and ciliated . At its See also:

• ATTACHMENT

attachment to the See also:

• BODY

body the groove sinks into the mouth . In• Bonellia the proboscis is forked at its See also:

• FREE

free end, but in the other genera it is See also:

• SHORT, FRANCIS JOB (1857– )

short and unforked . The body is somewhat sausage-shaped, with the anus at the pos-' terior extremity, . surrounded in Echiurus by a single or See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

double See also:

• RING (O.E. hring; a word common to Teutonic languages; and probably cognate with the Lat. circus, Gr. KtpKOS or KpLKOS, Skt'. chakra, wheel, circle, cf. also " harangue "); in art, a band of circular shape of varying sizes, made of any material and used f

ring of setae . The skin is usually wrinkled, and in B. viridis, Thalassema lankesteri, Th. baronii, Hamingia . 'arctica, B and in the larva of many. See also:

• SPECIES

species, is of a lively See also:

• GREEN, A
• GREEN, ALEXANDER HENRY (1832—1896)
• GREEN, DUFF (1791—1875)
• GREEN, JOHN RICHARD (1837—1883)
• GREEN, MATTHEW (1696-1737)
• GREEN, THOMAS HILL (1836-1882)
• GREEN, VALENTINE (1739–1813)
• GREEN, WILLIAM HENRY (.1825–1900)

green proboscis; b, mouth; c, ventral hooks; d, formed in true setal anus . sacs as in Chaeto- poda, project from the body a short distance behind the mouth, and are moved by See also:

• SPECIAL

special muscles; they are of use in helping the See also:

• ANIMAL
• ANIMAL (Lat. animalis, from anima, breath, soul)

animal to move slowly about, and they take a large See also:

• SHARE (O. Eng. scearu, chiefly in compounds, e.g. land-scearu, a share of land, from sceran to cut; cf. " shear" )

share in the burrowing movements (C .

B . See also:

• WILSON, ALEXANDER (1766-1813)
• WILSON, HENRY (1812–1875)
• WILSON, HORACE HAYMAN (1786–1860)
• WILSON, JAMES (1742—1798)
• WILSON, JAMES (1835— )
• WILSON, JAMES HARRISON (1837– )
• WILSON, JOHN (1627-1696)
• WILSON, JOHN (178 1854)
• WILSON, ROBERT (d. 1600)
• WILSON, SIR DANIEL (1816–1892)
• WILSON, SIR ROBERT THOMAS (1777—1849)
• WILSON, SIR WILLIAM JAMES ERASMUS
• WILSON, THOMAS (1663-1755)
• WILSON, THOMAS (c. 1525-1581)
• WILSON, WOODROW (1856— )

Wilson, Biol . See also:

• BULL
• BULL, GEORGE (1634–1710)
• BULL, JOHN (c. 1562–1628)
• BULL, OLE BORNEMANN (18ro-188o)

Bull., 1900), for some species See also:

• TUNNEL (Fr. tonne!, later tonneau, a diminutive from Low Lat. tonna, tunna, a tun, cask)

tunnel in the mud and See also:

• SAND
• SAND, GEORGE (1804-1876)

sand and See also:

• FORM (Lat. forma)

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 See also:

• APERTURE (from Lat. aperire, to open)

aperture through which the proboscis is extruded . This organ carefully searches the neighbourhood for particles of See also:

• FOOD
• FOOD (like the verb " to feed," from a Teutonic root, whence O. Eng. foda; cf. " fodder "; connected with Gr. lrareicOae, to feed)

food . When these are found the grooved proboscis folds its walls inwards, and the See also:

• CILIA (plural of Lat. cilium, eyelash)

cilia pass the particles down the See also:

• TUBE (Lat. tuba)

tube thus formed to the mouth . Echiuroids also move by extending the proboscis, which takes hold of some fixed See also:

• OBJECT

object, and, then contracting, draws the body for-wards . Recently it has been shown that Echiurus swims freely at See also:

• NIGHT

night-See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time, using for locomotion both the proboscis and the contraction of the muscles of its body-See also:

• WALL (O. Eng. weal, weall, Mid. Eng. wal, wane, adapted from Lat. vallum, rampart; the original O. Eng. word for a wall was wag or tenth)
• WALL, RICHARD (1694-1778)

wall . The See also:

• MOTION (Lat. motio, from movere, to move)
• MOTION, LAWS OF

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 . See also:

• ANATOMY
• ANATOMY (Gr. avaroyil, from ava-silo c', to cut up)

Anatomy (fig. z).—A thin cuticle covers the epidermis, which contains mucus-secreting glands .

Beneath, the epidermis is a layer a, Proboscis cut short. f, Ovary See also:

• BORNE, KARL LUDWIG (1786–1837)

borne on ventral See also:

• VESSEL (O. Fr. vaissel, from a rare Lat. vascellum, dim. of vas, vase, urn)

vessel b, Bristle passing through See also:

• RUNNING

running parallel with e . the mouth into the g, Position of anus . [nephridium . pharynx. h, Position of See also:

• EXTERNAL

external opening of c, Coiled See also:

• INTESTINE (Lat. intestinus, internal, usually in neuter plural intestina. from intus, within)

intestine. i, Nephridium — the See also:

• LINE

line points d, Anal tufts or vesicles. towards, but does not reach, e, Ventral See also:

• NERVE (Lat. nervus, Gr. vevpov, a bowstring)

nerve See also:

• CORD (derived through the Fr. corde, from the Lat. chorda, Gr. xop(5rt, the string of a musical instrument)

cord. the See also:

• INTERNAL

internal opening . of circular muscles, then a layer of See also:

• LONGITUDINAL

longitudinal, and finally in some cases a layer of oblique muscle-See also:

• FIBRES
• FIBRES (or FIBERS, in American spelling; from Lat. fibra, apparently connected either with filum, thread, or findere, to split)

fibres . The inner See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

face of this See also:

• MUSCULAR

muscular skin is lined by a layer of epithelium . Thecoelomic body-cavity is spacious . It does not extend into the proboscis, which is a solid organ traversed by the See also:

• NERVOUS

nervous and vascular rings, but otherwise largely built up of muscle fibres and connective See also:

• TISSUE (Fr. tissu, tissue, participle of tisser, Lat. texere, to weave)

tissue . Many sense-cells he in the epidermis . The ciliated ventral groove of the proboscis leads at its See also:

• BASE

base into the See also:

• SIMPLE

simple mouth, which gives See also:

• ACCESS (Lat. accessus)

access to the thin-walled alimentary See also:

• CANAL
• CANAL (from Lat. canalis, " channel " and " kennel " being doublets of the word)

canal . This is longer than the body, and to tuck it away it is looped from See also:

• SIDE
• SIDE (mod. Eski Adalia)

side to side . The loops are supported by strands of connective tissue, which in some species are See also:

• UNITED

united so as to form a dorsal mesentery, whilst traces of a ventral mesentery are met with anteriorly and posteriorly (H .

L . See also:

• JAMESON (or JAMESONE), GEORGE (c. 1587–1644)
• JAMESON, ANNA BROWNELL (1794-1860)
• JAMESON, LEANDER STARR (1853– )
• JAMESON, ROBERT (1774-1854)

Jameson, Zool . Jahrb . Anat., 1899) . The alimentary canal is divisible into fore-gut, See also:

• MID

mid-gut and See also:

• HIND

hind-gut, and the first-named can be further divided into pharynx, See also:

• OESOPHAGUS (Gr. o'lvca=I will carry, and r/)ayeiv, to eat)

oesophagus, gizzard and See also:

• CROP (a word common. in various forms, such as Germ. Kropf, to many Teutonic languages for a swelling, excrescence, round head or top of anything; it appears also in Romanic languages derived from Teutonic, in Fr. as troupe, whence the English " crupper "

crop, mainly on histological grounds . The mid-gut is characterized by the presence of a ciliated groove, from which arises the See also:

• COLLATERAL (from Med. Lat. collateralis,—cum, with, and latus, lateris, side,—side by side, hence parallel or additional)

collateral intestine or See also:

• SIPHON, or SYPHON (Lat. sipho; Gr. vi4xov, a tube)

siphon, a second tube which rejoins the alimentary canal See also:

• LOWER

lower down . Similar collateral intestines are See also:

• FAMILIAR (through the Fr. familier, from Lat. familiaris, of or belonging to the familia, family)

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 See also:

• MINUTE
• MINUTE (Lat. minutes, small; minuere, to make less)

minute ciliated funnels . The anal vesicles are thought to be excretory; whether this be so or not, they undoubtedly have some See also:

• INFLUENCE (Late Lat. influentia, from influere, to flow in)

influence on the amount of fluid found in the coelom . The coelomic fluid contains as a See also:

• RULE

rule both amoeboid and rounded corpuscles, and, when ripe, the products of the gonads . A closed See also:

• SYSTEM

system of vessels, usually called the vascular system, is See also:

• PRESENT

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 See also:

• MAIN (from the Aryan root which appears in " may " and " might," and Lat. magnus, great)
• MAIN (Lat. Moenus)

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 be- 4 hind, sends off a See also:

• BRANCH (from the Fr. branche, late Lat. branca, an animal's paw)

branch which forms a r i n g around the intestine and opens into the posterior extremity of the dorsal vessel .. In Echiurus and Thalassema the same vessel forms a ring See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round a stout muscle, which connects the bases of the two ventral setae before passing to surround the intestine . Am.oeboid corpuscles See also:

• FLOAT (in O. Eng. floc and flota, in the verbal form f eotan; the Teutonic root is flut-, another form of flu-, seen in " flow," cf. " fleet "; the root is seen in Gr. a-M e, to sail, Lat. pluere, to rain; the Lat, fluere and fluctus, wave, is not connect

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 See also:

• FUNNEL (through an O. Fr. founil, found in Breton, from Lat. infundibulum, that through which anything is poured, from fundere, to pour)

funnel-shaped nephrostomes . The posterior wall of the organ is produced into a See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long See also:

• BLIND, MATHILDE (1841—1896)

blind See also:

• SAC

sac, which is lined by secretory cells . The nervous system isa single ventral cord, which starts from a circumoesophageal ring . This ring is involved in the growth of the proboscis, and is See also:

• DRAWN

drawn out with it .

Thus there is a lateral nerve near each edge of the proboscis which unites with its See also:

• FELLOW

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 See also:

• REGULAR

regular intervals . The reproductive cells are modified coelomic cells, which See also:

• LIE, JONAS LAURITZ EDEMIL (1833—1908)
• LIE, MARIUS SOPHUS (1842–1899)

lie on the ventral vessel . They See also:

• ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

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 See also:

• FEMALE

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 See also:

• COMPANY

company of two or three others in a special See also:

• RECESS (Lat. recessus, a going back, withdrawal, from recedere, to withdraw)

recess of the nephridia of the female . Its structure may be gathered by a reference to fig . 3 . Larva.—The larva is a typical trochosphere, which, although of a temporary See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

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 persistsas the proboscis .

The sexes of the larvae are not determinable in the See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

early stages, but when a certain growth has been reached in Bonellia the See also:

• MALES

males seek the proboscis of the adult See also:

• FEMALES

females, and passing into the mouth undergo there the transformation into the planarian-like See also:

• PARASITE (From Gr. irapa, beside, Tiros food)

parasite which is the fully-formed male . This now creeps along the body of the female and takes up its See also:

• HOME
• HOME, DANIEL DUNGLAS (1833-1886)
• HOME, EARLS OF

home in her nephridia . See also:

• CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

Classification and See also:

• DISTRIBUTION (Lat. distribuere, to deal out)

Distribution.—The See also:

• ECHIUROIDEA (Gr: 'xis, adder, and ovpa, tail)

Echiuroidea consists of the following genera:-(1) Bonellia (Rol.), with four species. widely distributed, but inhabiting the temperate and warmer See also:

• WATERS, TERRITORIAL

waters of each hemisphere . (2) Echiurus (See also:

• GUERIN, JEAN BAPTISTE PAULIN (1783-1855)
• GUERIN, PIERRE NARCISSE, BARON (1774-1833)

Guerin-Meneville), with four species . This genus reaches from the See also:

• ARCTIC (Gr. "ApKroc, the Bear, the northern constellation of Ursa Major)

Arctic waters of both hemispheres into the cooler temperate regions . (3) Hamingia (Kor. and See also:

• DAN

Dan.). with one species, which has been taken in the Arctic See also:

• SEA (in O. Eng. sae, a common Teutonic word; cf. Ger. See, Dutch Zee, &c.; the ultimate source is uncertain)
• SEA, COMMAND OF THE

Sea and the Hardanger See also:

• FJORD, or FIORD

Fjord . (4) Saccosoma (Kor. and Dan.) was described from a single specimen dredged about half-way between See also:

• ICELAND (Dan. Island)

Iceland and See also:

• NORWAY
• NORWAY (Norge)

Norway . (5) 'Thalassema (Gaertner, See also:

• LAMARCK,

Lamarck), with twenty-one species . This genus is in the main a See also:

• DENIZEN (derived through the Fr. from Lat. de intus, " from within," i.e. as opposed to " foreign ")

denizen of the warmer waters of the globe . Sixteen species are found only in tropical or subtropical seas, three species are Mediterranean (Mt . Slat . Neapel, 1899), whilst three species are from the eastern See also:

• ATLANTIC

Atlantic, where the temperature is modified by the Gulf Stream (See also:

• SHIPLEY
• SHIPLEY, JONATHAN (1714-1788)

Shipley; see Willey's Zoological Results, See also:

• PART

part iii .

1899; Proc . Zool . See also:

• SOC

Soc . Lond., 1898, 1899; and CambridgeNatural History, ii.) . The following are found in the See also:

• BRITISH

British See also:

• AREA

area:—E. pallasii Guerin-Meneville), Th. neptuni (Gaertner), and Th. lankesteri (Herdman, Q.J.M.S., 1898) . A jfinities.—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 .