ICI  . 17FIG . 24.—See also:

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

Animal and See also:

• SHELL
• SHELL (O. Eng. scell, scyll, cf. Du. sceel, shell, Goth. skalja, tile; the word means originally a thin flake,. cf. Swed. skalja, to peel off; it is allied to " scale " and " skill," from a root meaning to cleave, divide, separate)

shell of Phorus exutus . a, Snout (not introversible). d, See also:

• PRO

Pro- and meso-See also:

• PODIUM (Gr. lr66tov, diminutive of ?roils, foot)

podium; to the right b, Cephalic tentacles. of this is seen the metapodium c, Right See also:

• EYE
• EYE (O. Eng. edge, Ger. Auge; derived from an Indo-European root also seen in Lat. oc-ulus, the organ of vision (q.v.)

eye. bearing the sculptured operculum . there is, strictly speaking, no invagination (emboly), but an over-growth (epiboly) of the smaller cells to enclose the larger . The See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general features of this See also:

• PROCESS

process and of the relation of the blastopore to mouth and anus have been explained in treating of the development of See also:

• MOLLUSCA

Mollusca generally . In such cases the blastopore may entirely See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

close, and both mouth and anus develop as new Ingrowths (stomodaeum and proctodaeum), whilst, according to the observations of N . Bobretzky, the closed blastopore may coincide in position with the mouth in some instances (Nassa, &c.), instead of with the anus . But in these epibolic forms, just as in the embolic Paludina, the embryo proceeds to develop its ciliated See also:

• BAND

band and shell-gland, passing through the earlier See also:

• CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition of a trochosphere to that of the veliger . In the veliger See also:

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

stage many Pectinibranchia (See also:

• PURPURA

Purpura, Nassa, &c.) exhibit, in the dorsal region behind the See also:

• HEAD (in 0. Eng. heafad; the word is common to Teutonic languages; cf. Dutch hoofd, Ger. Haupt, generally taken to be in origin connected with Lat. caput, Gr. KerbOvi7)
• HEAD, SIR EDMUND WALKER, BART
• HEAD, SIR FRANCIS BOND, BART

head, a contractile See also:

• AREA

area of the See also:

• BODY

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 . This acts as a larval See also:

• HEART
• HEART, LUNG

heart, but ceases to pulsate after a 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 . Similar rhythmically contractile a, Snout or rostrum. f, Operculum .

b, Cephalic tentacle. h',Prolonged siphonal notch of the c, Eye. shell occupied by the See also:

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

siphon, d, Propodium and mesopodium. or trough-like process of the e, Metapodium. See also:

• MANTLE

mantle-skirt . areas are found on the See also:

• FOOT

foot of the embryo Pulmonate Limax and on the yolk-See also:

• SAC

sac (distended foot-See also:

• SURFACE

surface) of the Cephalopod Loligo . The preconchylian invagination or shell-gland is formed in the embryo behind the velum, on the surface opposite the blastopore . It is surrounded by a See also:

• RIDGE (a word. common to many Teutonic languages, meaning " back," whether of a man or an animal, cf. German Rucke)
• RIDGE, WILLIAM PETT (1864- )

ridge of cells which gradually extends over the visceral sac and secretes the shell . In forms which are naked in the adult See also:

• STATE
• STATE, GREAT OFFICERS OF

state, the shell falls off soon after the reduction of the velum, but in Cenia, Runcina and Vaginula the shell-gland and shell are not See also:

• DEVELOPED

developed, and the See also:

• YOUNG
• YOUNG, A
• YOUNG, ARTHUR (1741-1820)
• YOUNG, BRIGHAM (1801-1877)
• YOUNG, CHARLES MAYNE (1777–1856)
• YOUNG, EDWARD (1683–1765)
• YOUNG, JAMES (1811-1883)
• YOUNG, THOMAS (1773-1829)

young animal when hatched has already the naked See also:

• FORM (Lat. forma)

form of the adult . One further feature of the development of the Pectinibranchia deserves See also:

• SPECIAL

special mention . Many See also:

• GASTROPODA

Gastropoda See also:

• DEPOSIT (Lat. depositurn, from deponere, to lay down, to put in the care of)

deposit their eggs, after fertilization, enclosed in capsules; others, as Paludina, are viviparous; others, again, as. the Zygobranchia, agree with the Lamellibranch h Conchifera (the bivalves) in having See also:

• SIMPLE

simple exits for the ova without glandular walls, and therefore See also:

• DISCHARGE (adapted from the O. Fr. discharge, modern decharge, from a med. Lat. discargare, to unload, dis- and earn care, to load, cf. " charge ")

discharge their eggs unenclosed in capsules freely into the 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-See also:

• WATER

water; such unencapsuled eggs are merely enclosed each in its own delicate chorion . When (After Lankester, 17.) dc, Directive corpuscle (outcast See also:

• CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell). f, Foot . ae, See also:

• ARCH
• ARCH, JOSEPH (1826– )

Arch-enteron or cavity lined by See also:

• MES

mes, Rudiments of the the enteric cell-layer or endo- skeleto-trophic tissues . derm. pi, The pedicle of invagina- bl, Blastopore. tion, the future rectum . vr, Velum or circlet of ciliated cells. shgl, The See also:

• PRIMITIVE

primitive shell-sac dv, Velar area or cephalic See also:

• DOME (Lat domus, house; Ital. duomo, cathedral)

dome. or shell-gland. sm, Site of the as yet unformed m, Mouth . mouth. an, Anus .

A, Diblastula phase (See also:

• OPTICAL

optical See also:

• SECTION
• SECTION (Lat. sectio, cutting, secare, to cut)

section) . B, The diblastula has become a trochosphere by the development of the ciliated 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 vr (optical section) . C, See also:

• SIDE
• SIDE (mod. Eski Adalia)

Side view of the trochosphere with commencing formation of the foot . D, Further advanced trochosphere (optical section) . E, The trochosphere passing to the veliger stage, dorsal view showing the formation of the primitive shell-sac . F, Side view of the same, showing foot, shell-sac (shgl), velum (vr), mouth and anus . N.B.—In this development the blastopore is not elongated; it persists as the anus . The mouth and stomodaeum form independently of the blastopore . See also:

• EGG (O.E. aeg, cf. Ger. Ei, Swed. aegg, and prob. Gr. u,ov, Lat. ovum)
• EGG, AUGUSTUS LEOPOLD (1816-1863)

egg-capsules are formed they are often of large See also:

• SIZE

size, have tough walls, and in each See also:

• CAPSULE (from the Lat. capsula, a small box)

capsule are several eggs floating in a viscid fluid . In some cases all the eggs in a capsule develop; in other cases one egg only in a capsule (Neritina), or a small proportion (Purpura, Buccinum), advance in development; the See also:

• REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest are arrested either after the first process of cell-See also:

• DIVISION (from Lat. dividere, to break up into parts, separate)

division (cleavage) or before that process . The arrested embryos or eggs are then swallowed and digested by those in the same capsule which have advanced in development . This is clearly the same process in essence as that of the formation of a vitellogenous gland from See also:

• PART

part of the primitive ovary, or of the feeding of an ovarian egg by the absorption of neighbouring potential eggs; but here the See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period at which the See also:

• SACRIFICE (from Lat. sacrificium; sacer, holy, and facere, to make)

sacrifice of one egg to another takes See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place is somewhat See also:

• LATE

late .

What it is that determines the See also:

• ARREST (Fr. arrester, arreeter, to stop or stay)

arrest of some eggs and the progressive development of others in the same capsule is at See also:

• PRESENT

present unknown . In the tribe of Pectinibranchia called Heteropoda the foot takes the form of a See also:

• SWIMMING (from " swim," A.S. swimman, the root being common in Teutonic languages)

swimming See also:

• ORGAN

organ . The See also:

• NERVOUS

nervous See also:

• SYSTEM

system and sense See also:

• ORGANS

organs are highly developed . The odontophore also is remarkably developed, its lateral See also:

• TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth being See also:

• MOBILE

mobile, and it serves as an efficient organ for attacking the other pelagic forms on which the Heteropoda See also:

• PREY (0. Fr. preie, mod. proie, Lat. praeda, booty, from prae and the root hed—seen in prehendere, prendere, to grasp)

prey . The sexes are distinct, as in all Streptoneura; and genital ducts and See also:

• ACCESSORY

accessory glands and pouches are present, as in all Pectinibranchia . The Heteropoda exhibit a See also:

• SERIES (a Latin word from serere, to join)

series of modifications in the form and proportions of the visceral See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass and foot, leading from a condition readily comparable with that of a typical Pectinibranch such as Rostellaria, with the three regions of the foot strongly marked and a coiled visceral hump of the usual proportions, up to a condition in which the whole body is of a tapering cylindrical shape, the foot a See also:

• PLATE

plate-like See also:

• VERTICAL (from Lat. vertex, highest point)

vertical fin, and the visceral hump almost completely atrophied . Three steps of this modification may be a, Mouth and odontophore. n, Dorsal surface overhung by b, Cephalic tentacles. the mantle-skirt; the See also:

• LETTER (through Fr. lettre from Lat. littera or litera, letter of the alphabet; the origin of the Latin word is obscure; it has probably no connexion with the root of linere, to smear, i.e. with wax, for an inscription with a stilus)

letter c, Eye. is close to the salivary gland . d, Propodium (B) and meso- o, Rectum and anus . podium. p, See also:

• LIVER (O. Eng. lifer; cf. cognate forms, Dutch lever, Ger. Leber, Swed. lefver, &c.; the O. H. Ger. forms are libara, lipora, &c.; the Teut. word has been connected with Gr. i'prap and Lat. jecur)

Liver . e, Metapodium. q, Renal organ (nephridium) . f, Operculum. s, Ventricle . h, Mantle-chamber. u, The otocyst attached to the i, Ctenidium (gill-plume). cerebral ganglion .

k, Retractor muscle of foot. w, Testis . 1, Optic tentacle. x, See also:

• AURICLE (from Lat. diminutive of auris, ear)

Auricle of the heart . m, See also:

• STOMACH (Gr. vrbsaxos from arbga, a mouth)

Stomach. y, Vesicle on genital duct. z, Penis . distinguished as three families:—Atlantidae, Carinariidae and Pterotrachaeidae . They are true Pectinibranchia which have taken to a pelagic See also:

• LIFE

life, and the peculiarities of structure which they exhibit are strictly adaptations consequent upon their changed mode of life . Such adaptations are the transparency and colourlessness of the tissues, and the modifications of the foot, which still shows in See also:

• ATLANTA

Atlanta the form See also:

• COMMON

common in Pectinibranchia (compare fig . 27 and fig . 24) . The cylindrical body of Pterotrachaea is paralleled by the slug-like forms of Euthyneura . J . W . Spengel has shown that the visceral See also:

• LOOP

loop of the Heteropoda is streptoneurous .

Special to the Heteropoda is the high elaboration of the lingual ribbon, and, as an agreement with some of the opisthobranchiate Euthyneura, but as a difference from the Pectinibranchia, we find the otocysts closely attached to the cerebral ganglia . This is, however, less of a difference than it was at one time supposed to be, for it has been shown by H . Lacaze-Duthiers, and also by F . Leydig, that the otocysts of Pectinibranchia even when lying close upon the pedal ganglion (as in fig . 21) yet receive their special See also:

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

nerve (which can sometimes be readily isolated) from the cerebral ganglion (see fig . I I) . Accordingly the difference is one of position of the otocyst and not of its nerve-See also:

• SUPPLY (through Fr. from Lat. supplere, to fill up)

supply . The Heteropoda are further remarkable for the high development of their cephalic eyes, and for the typical See also:

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

character of their osphradium (Spengel's olfactory organ) . This is a groove, the edges of which are raised and ciliated, lying near the branchial plume in the genera which possess that organ, whilst in Firoloida, which has no branchial plume, the osphradium occupies a corresponding position . Beneath the ciliated groove is placed an elongated ganglion (olfactory ganglion) connected by a nerve to the supra-intestinal (therefore the primitively dextral) ganglion of the See also:

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

long visceral nerve-loop, the strands of which See also:

• CROSS

cross one another—this being characteristic of Streptoneura (Spengel) . The Heteropoda belong to the " pelagic See also:

• FAUNA

fauna " occurring near the surface in the Mediterranean and See also:

• GREAT

great oceans in See also:

• COMPANY

company with the See also:

• PTEROPODA

Pteropoda, the Siphonophorous See also:

• HYDROZOA

Hydrozoa, Salpae, Leptocephali, and other specially-modified transparent swimming representatives a, Mouth and odontophore . b, Cephalic tentacles .

c, Eye . d, The fin-like metopodium. d', Its sucker . e, Metapodium . f, Salivary glands . of various See also:

• GROUPS
• GROUPS, THEORY

groups of the animal See also:

• KINGDOM

kingdom . In development they pass through the typical trochosphere and veliger stages provided with See also:

• BOAT (0. Eng. bdt; the true etymological connexion with Dutch and Ger. boot, Fr. bateau, Ital. battello presents great difficulties; Celtic forms are from O. Eng.)

boat-like shell . Sub-See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

order I.—TAENIOGLOSSA . Radula with a median tooth and three teeth on each side of it . See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

Formula 3 : i : 3 . Tribe I.—PLATYPODA . Normal Taenioglossa of creeping See also:

• HABIT (through the French from Lat. habitus, from habere, to have, hold, or, in a reflective sense, to be in a certain condition; in many of the English senses the French use habitude, not habit)

habit . The foot is flattened ventrally, at all events in its anterior part (Strombidae) .

Otocysts situated close to the pedal nerve-centres . Accessory organs are rarely found on the genital ducts, but occur in Paludina, Cyclostoma, Naticidae, Calyptraeidae, &c . Mandibles usually present . This is the largest See also:

• GROUP

group of Mollusca, including nearly sixty families, some of which are insufficiently known from the anatomical point of view . See also:

• FAIN, AGATHON JEAN FRANCOIS (1778–1837)

Fain. i.—Peludinidae . Pedal centres in the form of ganglionated cords; See also:

• KIDNEY

kidney provided with a ureter; viviparous; fluviatile . Paludina . Neothauma, from See also:

• LAKE
• LAKE, GERARD LAKE, 1ST VISCOUNT (1744-1808)

Lake See also:

• TANGANYIKA (a name said by V. L. Cameron to signify a " mixing-place ")

Tanganyika . Tylopoma, See also:

• EXTINCT

extinct, See also:

• TERTIARY

Tertiary . Fain . 2.—Cyclophoridae . No ctenidium, pallial cavity trans-formed into a See also:

• LUNG

lung; See also:

• APERTURE (from Lat. aperire, to open)

aperture of shell circular; terrestrial .

snout when retracted. i, See also:

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

Intestine . c, Pericardium. n, So-called See also:

• NUCLEUS (Lat. for the kernal of a nut, nux, the stone of fruit)

nucleus . ph, Pharynx. br, Branchial plume (ctenidium) oc, Cephalic eye. w, Osphradium . g, Cerebral ganglion. mt, Foot (metapodium) . g', Pleuro-pedal ganglion . , Caudal appendage. pr, Foot (metopodium) . Pomatias, shell turriculated . Diplommatina . Hybocystis . Cyelobhorus, shell umbilicated, with a See also:

• SHORT, FRANCIS JOB (1857– )

short See also:

• SPIRE

spire and horny operculum . Cyclosurus, shell uncoiled . Dermatocera, foot with a See also:

• HORN
• HORN (a common Teutonic word, cognate with Lat. cornu; cf. Gr. Kipas)
• HORN (Lat. cornu; corresponding terms being Fr. cor, trompe; Ger. Horn; Ital. corno)
• HORN, ARVID BERNHARD, COUNT (1664-1742)
• HORN, PHILIP DE MONTMORENCY, COUNT

horn-shaped protuberance at its posterior end .

Sj-iraculum . Fain . 3.—Ampullariidae . To the See also:

• LEFT

left of the ctenidium a pulmonary sac, separated from it by an incomplete septum, am- phibious . Ampullaria, shell dextral, coiled . sinistral, spire short or obsolete . Meladomus . Fain . 4.—Littorinidae . Oesophageal pouches present; pedal nerve-centres concentrated; a pedal penis near the right tentacle . Littorina, shell not umbilicated, littoral habit . Lacuna, foot with two posterior appendages, marine, entirely aquatic .

Cremnoconchus, entirely aerial, See also:

• INDIAN

Indian . Risella . Tectarius . Fam . 5.—Fossaridae . Head with two lobes in some Rhipidoglossa . Fossaria . Fain . 6.—Purpurinidae, extinct . Fain . 7 . Planaxidae .

Shell with pointed spire; a short pallial siphon . Planaxis . Fam . 8.—Cyclostomatidae . Pallial cavity transformed into a lung; pedal centres concentrated; a deep pedal groove . Cyclostoma, shell turbinated, operculum calcareous, See also:

• BRITISH

British . Omphalotropis . Fain . 9 . Aciculidae . Pallial cavity transformed into a lung; operculum horny; shell narrow and elongated . Acicula .

Fam. io.—Valvatidae . Ctenidium bipectinate, See also:

• FREE

free; hermaphrodite; fluviatile . Valvata, British . Fain. i i.—Rissoidae . Epipodial filaments present; one or two pallial tentacles . Rissoa . Rissoina . Stiva . Fain . 12 . Litiopidae . An epipodium bearing three pairs of tentacles and an operculigerous See also:

• LOBE

lobe with two appendages; inhabitants of the Sargasso See also:

• WEED, THURLOW (1797—1882)

weed .

Litiopa . Fam . 13 . Adeorbiidae . Mantle with two posterior appendages; ctenidium large and capable of protrusion from pallial cavity . A deorbis, British . Fam . 14.—Jeffreysiidae . Head with two long labial palps; shell ovoid; operculum horny, semicircular, carinated . Jeffreysia . Fain. t5 . Homalogyridae .

Shell flattened; no cephalic tentacles . Homalogyra, British . Ammoniceras . Fam. i6.—Skeneidae . Shell depressed, with rounded aperture; cephalic tentacles long . Skenea, British . Fain . 17.—Choristidae . Shell See also:

• SPIRAL

spiral; four cephalic tentacles; eyes absent ; two pedal appendages, Choristes . Fam . 18 . Assimineidae .

Eyes at free extremities of tentacles . Assiminea, estuarine, British . Fam . 19.—Truncatellidae . Snout very long, bilobed; foot short . Truncatella . Fam . 2o.—Hydrobiidae . Shell with distant from right tentacle, generally appendiculated; brackish water or fluviatile . Hydrobia, British . Baikalia, from Lake See also:

• BAIKAL (known to the Mongols as Dalai-nor, and to the Turkish tribes as Bai-kul)

Baikal . Pomatiopsis .

Bithynella . Lithoglyphus . Spekia, viviparous, from Lake Tanganyika . Tanganyicia . Limnotrochus, from Lake Tanganyika . Chytra . Littorinida . See also:

• BITHYNIA (BtOvpta)

Bithynia, British, fluviatile . Stenothyra . Fam . 21.—Melaniidae . Spire of shell somewhat elongated; mantle-border fringed; viviparous; fluviatile .

Melania . See also:

• FAUNUS (i.e. the "kindly," from Lat. favere, or the " speaker," from fari)

Faunus . Paludomus . Melanopsis . Nassopsis . Bythoceras, from Lake Tanganyika . Fam . 22.—Typhobiidae . Foot wide ; shell turriculated, with carinated whorls, the carinae tuberculated or spiny . Typhobia . Bathanalia, from Lake Tanganyika . Fain .

23 . Pleuroceridae . Like Melaniidae, but mantle-border not fringed and See also:

• REPRODUCTION

reproduction oviparous . Pleurocera . Anculotus . Fain . 24.—Pseudomelaniidae . All extinct . Fam . 25.—Subulitidae . All extinct . Fam .

26.—Nerineidae . All extinct . Fam . 27.—Cerithiidae . Shell with numerous tuberculated whorls ; aperture canaliculated anteriorly; short pallial siphon . Ceri- thium . Bittium . Potamides . Triforis . Laeocochlis . Ceri- thiopsis . Fam .

28.—Modulidae . Shell with short spire; no siphon . Modulus . Lanistes, shell a A, The animal . B, The shell removed . C, D, Two views of the shell of Cardiopoda . h, Border of the mantle-flap. u, Cerebral ganglion . i, Ctenidium (gill-plume). v, Pleural and pedal ganglion m, Stomach. w, Testis . n, Intestine. x, Visceral ganglion . o, Anus. y, Vesicula seminalis . p, Liver . [ventricle. z, Penis. t, Aorta, springing from the prominent spire ; penis 0 o, Mouth .

op, Operculum . br, Ctenidium (branchial plume) . x, Filiform appendage (? rudimentary ctenidium) . The freely projecting ctenidium of typical form not having its See also:

• AXIS (Lat. for " axle ")

axis fused to the roof of the branchial chamber is the notable character of this genus . Fam . 29.—Vermetidae . Animal fixed by the shell, the last whorls of which are not in contact with each other; foot small; two anterior pedal tentacles . Vermetus . Siliquaria . Fam . 3o.—Caecidae . Shell almost completely uncoiled, in one See also:

• PLANE

plane, with See also:

• INTERNAL

internal septa .

Caecum, British . Fain . 31.—Turritellidae . Shell very long; head large; foot broad . Turritella, British . Mesalia . Mathilda . Fam . 32.—Struthiolariidae . Shell conical ; aperture slightly canaliculated ; siphon slightly developed . Struthiolaria . Fam .

33.—Chenopodidae . Shell elongated; aperture See also:

• EXPANDED

expanded; siphon very short . Chenopus, British . A l o r i a, Spinigera, Diartema, extinct . Fam . 34 . Slrombidae . Foot narrow, compressed, without See also:

• SOLE (Solea)

sole . Strombus . Pteroceras . Rostellaria . Terebellum .

Fam . 35.—Xenophoridae . Foot transversely divided into two parts . Xenophorus . Eotrochus, See also:

• SILURIAN

Silurian . Fam . 36.—Capulidae . Shell conical, not FIG . 31.—Shell of Crucibulum, seen coiled,butslightlyin- from below so as to show the inner whorl curved posteriorly; b, concealed by the cap-like See also:

• OUTER

outer whorl a. atongue-shaped See also:

• PROJECTION

projection between snout and foot . Capulus . Thyca, parasitic on asterids . Platyceras, extinct .

Fam . 37 . Hipponycidae . Shell conical; foot secreting a ventral calcareous plate; animal fixed . Hipponyx . Mitrularia . Fam . 38.—Calyptraeidae . Shell with short spire; lateral cervical lobes present; accessory genital glands . Calyptraea, British . Crepidula . Crucibulum .

Fam . 9.—Naricidae . Foot divided into two, posterior See also:

• HALF

half bearing the operculum; a wide epipodial velum; shell turbinated . Narica . Fain . 4o.—Naricidae . Foot large, with aquiferous system; propodium reflected over head; eyes degenerate; burrowing habit . Natica, British . Amaura . Sigaretus . Fam . 41.—Lamellariidae .

Shell thin, more or less covered by the mantle; no operculum . Lamellaria . Velutina . Marsenina, Oncidiopsis, hermaphrodite . Fain . 4z.—Trichotropidae . Shell with short spire, carinate and pointed . Trichotropis . Fam . 43.—Seguenziidae . Shell trochiform, with canaliculated aperture and See also:

• TWISTED

twisted See also:

• COLUMELLA, LUCIUS JUNIUS MODERATUS

columella . Seguenzia, abyssal .

Fam . 44.—Janthinidae . Shell thin; operculum absent; tentacles bifid; foot secretes a 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; pelagic . Janthina . Recluzia . Fam . 45.—Cypraeidae . Shell inrolled, solid, polished, aperture very narrow in adult; short siphon; anus posterior ; osphradium with three lobes; mantle reflected over shell . Cypraea . Pustularia . Ovula . Pedicularia, attached to See also:

• CORALS (KoRAis), ADAMANTIOS [in French, DIAMANT CORAY] (1748–1833)

corals .

Erato . Fam . 46.—Tritonidae . Shell turriculated and siphonated, thick, each whorl with varices; foot broad and truncated anteriorly; pallial siphon well developed; See also:

• PROBOSCIS

proboscis present . See also:

• TRITON

Triton . Per- sona . Ranella . Fain . 47.—Columbel- linidae . All extinct . Fam . 48.—Cassididae .

Shell ventricose,with elongated aperture, J and short spire; proboscis and siphon long ;operculum with marginal nucleus . Cassis . Cassidaria . Oniscia . Fam.49—Oocorythidae . Shell globular and ventricose; aperture See also:

• OVAL (Lat. ovum, egg)

oval and canaliculated; operculum spiral . Oocorys, abyssal . Fam . 50 . Doliidae . Shell ventricose, with short spire, and wide aperture; no varices and no operculum; foot very broad, with projecting anterior angles; siphon long . Dolium .

Pyrula . Fam . 51.—Solariidae . Solarium . Torinia . Fluxina . Fam . 52.—Scalariidae . Shell turriculated, with elongated spire; proboscis short; siphon rudimentary . Scalaria . Eglisia . Crossea .

Aclis . The three following families have neither radula nor jaws, and are therefore called Aglossa . They have a well-developed proboscis which is used as a suctorial organ; some are abyssal, but the See also:

• MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority are either commensals or parasites of Echinoderms . Fam . 53.—Pyramidellidae . See also:

• SUMMIT

Summit of spire heterostrophic; a projection, the mentum, between head and foot; operculum present . Pyramidella . Turbonilla . Odostomia, British . Myxa . Fam . 54 .

Eulimidae . Visceral mass still coiled spirally; shell thin and shining . Eulima, foot well developed, with an operculum, animal usually free, but some live in the See also:

• DIGESTIVE

digestive cavity of Holothurians . Mucronalia, foot reduced, but still operculate, eyes present, animal fixed by its very long proboscis which is deeply buried in the tissues of an Echinoderm, no pseudopallium . Styl fer, the operculum is lost, animal fixed by a large proboscis which forms a pseudopallium covering the whole shell except the extremity of the spire, parasitic on all groups of Echinoderms . Entosiphon, visceral mass still coiled; shell much reduced, proboscis very long forming a pseudopallium which covers the whole body and projects beyond in the form of a siphon, foot and nervous system present, eyes, branchia and anus absent, See also:

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

parasite in the Holothurian Deima blakei in the Indian Ocean . Fam . 55.—Entoconchidae . No shell ; visceral mass not coiled ; no sensory organs, nervous system, branchia or anus; body reduced to a more or less tubular sac; hermaphrodite and viviparous; parasitic in Holothurians; larvae are veligers, with shell and operculum . Entocolax, mouth at free extremity, animal fixed by aboral orifice of pseudopallium, Pacific . Entoconcha, body elongated and tubular, animal fixed by the oral extremity, protandric hermaphrodite, parasitic in testes of Holothurians causing their See also:

• ABORTION (from Lat. aboriri, to fail to be born, or perish)

abortion . Enteroxenos, no pseudo- See also:

• PALLIUM

pallium and no intestine, hermaphrodite, larvae with operculum .

Tribe 2.—HETEROPODA . Pelagic Taenioglossa with foot large and laterally compressed to form a fin . Fam . 1 . Atlantidae . Visceral sac and shell coiled in one plane; foot divided transversely into two parts, posterior part bearing an operculum, anterior part forming a fin provided with a sucker . Atlanta . Oxygyrus . Fain . 2.—Carinariidae . Visceral sac and shell small in proportion to the rest of the body, which cannot be withdrawn into the shell; foot elongated, fin-shaped, with sucker, but without operculum . Carinaria .

Cardiopoda . Fam . 3.—Pterotrachaeidae . Visceral sac very much reduced; without shell or mantle; anus posterior; foot provided with sucker in male only . Pterotrachaea . Firoloida . Pterosoma . Sub-order 2.—STENOGLOSSA . Radula narrow with one lateral tooth on each side, and one median tooth or none . Tribe I.—RACHIGLOSSA . Radula with a median tooth and a single b, egg-capsules; c, ctenidium (gill-plume); d, cephalic tentacles . tooth on each side of it .

Formula 1 : 1 : 1 . Rudimentary jaws present . Fain . I.—Turbinellidae . Shell solid, piriform, with thick folded columella; lateral teeth of radula bicuspidate . Turrinella . Cynodonta . Fulgur . Hemifusus . Tudicla . Strepsidura . Fain .

2.—Fasciolariidae . Shell elongated, with long siphon; lateral teeth of radula multicuspidate . Fasciolaria . Fusus . Clavella . Latirus . Fam . 3.—Mitridae . Shell fusiform and solid, aperture elongated, columella folded; no operculum; eyes on sides of tentacles . See also:

• MITRA, RAJENDRA LALA (1824-1891)

Mitra . Turricula . Cylindromitra .

Imbricaria . Fam . ,4.—Buccinidae . Foot large and broad ; eyes at See also:

• BASE

base of d, Foot . h, Mantle-skirt, which is naturally carried in a reflected condition so as to See also:

• COVER (from the Fr. convert, from couvrir, to cover, Lat. cooperire)

cover the sides of the shell . a, See also:

• APEX

Apex . ac, Siphonal notch of the mouth of the shell . ac to pc, Mouth of the shell. w, w, Whorls of the shell. s, s, Sutures . Occupying the axis, and exposed by the section, is seen the columella " or spiral See also:

• PILLAR (0. Fr. piler, Mod. pilier, Late Lat. pilare, from pila, column)

pillar . The upper whorls of the shell are seen to be divided into See also:

• SEPARATE

separate See also:

• CHAMBERS (the Fr. chambre, from Lat. camera, a room)
• CHAMBERS, EPHRAIM (d. 1740)
• CHAMBERS, GEORGE (1803-1840)
• CHAMBERS, ROBERT (18oz-1871)
• CHAMBERS, SIR WILLIAM (1726-1796)

chambers by the formation of successively formed " septa.” ,;V'o 00.004i!44 444ioniusl144,uthp tentacles ; operculum horny . Buccinum . Chrysodomus .

Liomesus . Cominella . Tritonidea . Pisania . Euthria . Phos . D~spsacus . Fam . 5.—Nassidae . Foot broad, with two slender posterior appendages; operculum unguiculate . Nassa, marine, British . Canidia, fluviatile .

Bullia . Fain . 6.—Muricidae . Shell with moderately long spire and See also:

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

canal, ornamented with ribs, often spiny; foot truncated anteriorly . Murex, British . Trophon, British . Typhis . Urosalpinx . Lachesis . Fain . 7 . Purpurulae .

Shell thick, with short spire, last whorl large and canal short; aperture wide; operculum horny . Purpura, British . Rapana . Monoceros . See also:

• SISTRUM (Gr. veia'rpov, Ger. Rappel)

Sistrum . Concholepas . Fain . 8.—Haliidae . Shell ventricose, thin and smooth, with wide aperture; foot large and thick, without operculum . Halia . Fam. q.—Cancellarizdaa . Shell ovoid, with short spire and folded columella; foot small, no operculum; siphon short .

Can- cellaria . Fam. io.—Columbellidae . Spire of shell prominent, aperture narrow, canal very short, columella crenelated; foot large . Columbella . Fain. it.—Coralliophilidae . Shell irregular; radula absent; foot and siphon short; sedentary animals, living in corals . Coralliophila . Rhizochilus . Lepioconchus . Magilus . Rapa . Fam. t2.—Volutidae .

Head much flattened and wide, with eyes on sides; foot broad; siphon with internal appendages . Voluta . Guivillea . Cymba . Fain . 13.- Olividae . Foot with anterior transverse groove; a posterior pallial tentacle; generally burrowing . Olivia . Olivella . Ancillaria . Agaronia . Fam. t4.—Marginellidae .

Foot very large; mantle reflected over shell . Marginella . Pseudomarginella . Fain . 15.—Harpidae . Foot very large; without operculum; shell with short spire and See also:

• LONGITUDINAL

longitudinal ribs; siphon long . Har pa . Tribe z.—TOXIGLOSSA . No jaws . No median tooth in radula . Formula : t : o : t . See also:

• POISON

Poison-gland present whose duct traverses the nerve-See also:

• COLLAR

collar .

Fain. t.--Pleurotomatidae . Shell fusiform, with elongated spire; margin of shell and mantle notched . Pleurotoma . Clavatula . Mangilia . See also:

• BELA
• BELA, LAS BELA

Bela . Pusionella . Pontiothauma . Fain. z.—Terebridae . Shell turriculated, with numerous whorls; aperture and operculum oval; eyes at summits of tentacles; siphon long . Terebra . Fain .

3.—Conidae . Shell conical, with very short spire, and narrow aperture with parallel See also:

• BORDERS, THE

borders; operculum unguiform . Cones . Sub-Class II.—EuTHYNEURA The most important general character of the Euthyneura is the See also:

• ABSENCE (Lat. absentia)

absence of torsion in the visceral commissure, and the more posterior position of the anus and pallial organs . See also:

• COMPARATIVE

Comparative See also:

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

anatomy and See also:

• EMBRYOLOGY

embryology prove that this condition is due, not as formerly supposed to a difference in the relations of the visceral commissure which prevented it from being included in the torsion of the visceral hump, but to an actual detorsion which has taken place in See also:

• EVOLUTION

evolution and is repeated to a great extent in individual development . In several of the more primitive forms the same torsion occurs as in Streptoneura, viz. in See also:

• ACTAEON

Actaeon and Limacina among Opisthobranchia, and Chilina among Pulmonata . Actaeon is prosobranchiate, the visceral commissure is twisted in Actaeon and Chilina, and even slightly still in Bulla and Scaphander; in Actaeon and Limacina the osphradium is to the left, innervated by the supra-intestinal ganglion . But in the other members of the sub-class the detorsion of the visceral mass has carried back the anus and circumanal complex from the anterior dorsal region to the right side, as in Bulla and Aplysia, or even to the posterior end of the body, as in Philine, Oncidium, See also:

• DORIS

Doris, &c . Different degrees of the same process of detorsion are, as we have seen, exhibited by the Heteropoda among the Streptoneura, and both in them and in the Euthyneura the detorsion is associated with degeneration of the shell . Where the modification is carried to its extreme degree, not only the shell but the pallfal cavity, ctenidium and visceral hump disappear, and the body acquires a simple elongated form and a secondary See also:

• EXTERNAL

external symmetry, as in Pterolrachaea and in Doris, Eolis, and other Nudibranchia . These facts afford strong support to the hypo-thesis that the See also:

• WEIGHT

weight of the shell is the See also:

• ORIGINAL

original cause of the torsion of the dorsal visceral mass in Gastropods . But this See also:

• HYPOTHESIS (from Gr. inrorcOivat, to put under; cf. Lat. suppositio, from sub-ponere)

hypothesis leaves the See also:

• ELEVATION

elevation of the visceral mass and the exogastric coiling of the shell in the ancestral form unexplained .

(Formula, x.l.x.) radula has a number of See also:

• UNIFORM

uniform teeth on each side of the median tooth in each transverse See also:

• ROW, JOHN (c. 1525—1580)

row . The head in most cases bears two pairs of tentacles . All the Euthyneura are hermaphrodite . In the most primitive condition the genital duct is single throughout its length and has a single external aperture; it is therefore said to be monaulic . The hermaphrodite aperture is on the right side near the opening of the pallial cavity, and a ciliated groove conducts the spermatozoa to the penis, which is situated more anteriorly . This is the condition in the Bullomorpha, the Aplysiomorpha, and in one Pulmonate, Pythia . In some cases while the original aperture remains undivided, the seminal groove is closed and so converted into a canal . This is the modification found in Cavolinia longirostris among the Bullomorpha, and in all the Auriculidae except Pythia . A further degree of modification occurs when the male duct takes its origin from the hermaphrodite duct above the external opening, so that there are two distinct apertures, one male and one See also:

• FEMALE

female, the latter being the original opening . The genital duct is now said to be diaulic, as in Valvata, Oncidiopsis, Actaeon, and Lobiger among the Bullomorpha, in the Pleurobranchidae, in the Nudibranchia, except the Doridomorpha and most of the Elysiomorpha, and in the Pulmonata . Originally in this condition the female aperture is at some distance from the male, as in the Basommatophora and in other cases; but in some forms the female aperture itself has shifted and come to be contiguous with the male opening and penis as in the Stylommatophora . In all these cases the female duct bears a bursa copulatrix or receptaculum seminis .

In some forms this receptacle acquires a separate external opening remaining connected with the oviduct internally . There are thus two female openings, one for copulation, the other for oviposition, as well as a male opening . The genital duct is now trifurcated or triaulic, a condition which is confined to certain Nudibranchs, viz. the Doridomorpha and most of the Elysiomorpha . The Pteropoda, formerly regarded as a distinct class of the Mollusca, were interpreted by E . R . Lankester as a See also:

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

branch of the See also:

• CEPHALOPODA

Cephalopoda, chiefly on See also:

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

account of the protrusible sucker-bearing processes at the anterior end of Pneumonoderma . These he considered to be homologous with the arms of Cephalopods . He fully recognized, however, the similarity of Pteropods to Gastropods in their general asymmetry and in the torsion of the visceral mass in Limacinidae . It is now understood that they are Euthyneurous Gastropods adapted to natatory locomotion and pelagic life . The sucker-bearing processes of Pneumonos See also:

• DERMA

derma are outgrowths of the proboscis . The fins of Pteropods are now interpreted as the expanded lateral margins of the foot, termed parapodia, not homologous with the siphonof Cephalopods which is formed from epipodia . The Thecosomatous Pteropoda are allied to Bulla, the Gymnosomatous forms to Aplysia .

The Euthyneura comprises two orders, Opisthobranchia and Pulmonata . In those Euthyneura in which the shell is entirely absent in the adult, it is, except in the three genera Cenia, Runcina and Vaginula, developed in the larva and then falls off . In other cases (Tectibranchs) the reduced shell is enclosed by upgrowths of the edge of the mantle and becomes internal, as in many Cephalopods . A few Euthyneura in which the shell is not much reduced retain an operculum in the adult state, e.g . Actaeon, Limacina, and the marine Pulmonate, A mphibola . The detorted visceral commissure shows a tendency to the concentration of all its elements See also:

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

round the See also:

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

oesophagus, so that except in the Bullomorpha and in Aplysia the. whole nervous system is aggregated in the cephalic region, either dorsally or ventrally . The Order I.—OPISTHOBRANCHIA . Marine Euthyneura, the more archaic forms of which have a relatively large foot and a small visceral hump, from the base of which projects on the right side a short mantle-skirt . The anus is placed in such forms far back beyond the mantle-skirt . In front of the anus, and only partially covered Y A, Veliger-larva of an Opisthobranch (Polycera). f, Foot; op. operculum; mn, anal papilla; ry, dry, two portions of unabsorbed nutritive yolk on either side of the intestine . The right otocyst is seen at the See also:

• ROOT (late O.E. rot, adopted from Scand., cf. Norw. and Swed. rot, Dan. rod; the true O.E. word was wyrt, plant, represented in Ger. Wurz or Wurzel; the ultimate root is the same in both words, and is seen in Lat. radix)
• ROOT, ELIHU (1845– )

root of the foot . B, Trochosphere of an Opisthobranch (Pleurobranchidium) showing—shgr, the shell-gland or primitive shell-sac; v, the See also:

• CILIA (plural of Lat. cilium, eyelash)

cilia of the velum; ph, the commencing stomodaeum or oral invagination; ot, the left otocyst; pg, red-coloured pigment spot .

C, Diblastula of an Opisthobranch (Polycera) with elongated blastopore oi . (All from Lankester.) by the mantle-skirt, is the ctenidium with its free end turned back-wards . The heart lies in front of, instead of to the side of, the See also:

• ATTACHMENT

attachment of the ctenidium—hence Opisthobranchia as opposed to " Prosobranchia," which correspond to the Streptoneura . A shell is possessed in the adult state by but few Opisthobranchia, but all pass through a veliger larval stage with a nautiloid shell (fig . 36) . Many Opisthobranchia have by a process of See also:

• ATROPHY (Gr. It- priv., rpo4, nourishment)

atrophy lost the typical ctenidium and the mantle-skirt, and have developed other organs in their place . As in some Pectinibranchia, the free margin of the mantle-skirt is frequently reflected over • the shell when a shell exists; and, as in some Pectinibranchia, broad lateral outgrowths of the foot (parapodia) are often developed which may be thrown over the shell or naked dorsal surface of the body . The variety of special developments of structure accompanying the atrophy of typical organs in the Opisthobranchia and general degeneration of organization is very great . The members of the order present the same wide range of superficial appear- ance as do the Pectini- branchiate Streptoneura, forms carrying well-de- veloped spiral shells and large mantle-skirts being included in the group, together with flattened or cylindrical slug-like forms . But in respect of the sub- stitution of other parts for the mantle-skirt and for . the gill which the more degenerate Opisthobranchia exhibit, this order stands alone . Some Opisthobranchia are striking examples of de- See also:

• GENERATION (from Lat. generare, to beget, procreate; genus, stock, race)

generation (some Nudibranchia), having none of those regions or processes of the body developed which distinguish the archaic Mollusca from such See also:

• FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat-See also:

• WORMS

worms as the Dendrocoel See also:

• PLANARIANS

Planarians .

In- See also:

• DEED (in O. Eng. dead, from the stem of the verb " to do ")

deed, were it not for their retention of the characteristic odontophore we should have little or no indication that such forms as Phyllirhoe and Limapontia really belong to the Mollusca at all . The interesting little Rhodope veranyii, which has no odontophore, has been associated by systematists both with these simplified Opisthobranchs and with Rhabdocoel Planarians . In many respects the sea-See also:

• HARE
• HARE, SIR JOHN (1844– )

hare (Aplysia), of which several See also:

• SPECIES

species are known (some occurring on the See also:

• ENGLISH

English See also:

• COAST (from Lat. costa, a rib, side)

coast), serves as a convenient example of the fullest development of the organization characteristic of Opisthobranchia . The woodcut (fig . 38) gives a faithful See also:

• REPRESENTATION

representation of the great mobility of the various parts of the body . The head is well marked and joined to the body by a somewhat constricted See also:

• NECK (O. Eng. hnecca; the word appears in many Teutonic languages; cf. Dutch ride, Ger. Nacken; in O. E. the common word was heals; cf. Ger. Hals)

neck . It carries two pairs of cephalic tentacles and a pair of sessile eyes . The visceral hump is See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low and not See also:

• DRAWN

drawn out into a spire . The foot is long, carrying the oblong visceral mass upon it, and projecting (as metapodium) a little beyond it(f) . Later-ally the foot gives rise to a pair of mobile fleshy lobes, the parapodia (ep), which can be thrown up so as to cover in the dorsal surface of the animal . Such parapodia are common, though by no means universal, among Opisthobranchia . The torsion of the visceral hump is not carried out very fully, the consequence being that the anus has a posterior position a little to the right of the median See also:

• LINE

line above the metapodium, whilst the branchial chamber formed by the overhanging mantle-skirt faces the right side of the body instead of lying well to the front as in Streptoneura and as in Pulmonate Euthyneura .

The gill-plume,which in A plysia is the typicalMolluscan ctenidium, is seen in fig . 39 projecting from the branchial sub-pallial space . C 1, Anterior cephalic tentacles. m, Mantle-flap reflected over the t2, Posterior cephalic tentacles. thin oval shell . e, Eyes. os, s, Orifice formed by the un- f, Metapodium. closed border of the reflected ep, Epipodium. mantle-skirt, allowing the g, Gill-plume (ctenidium). shell to show. pe, The spermatic groove . The relation of the delicate shell to the mantle is See also:

• PECULIAR

peculiar, since it occupies an oval area upon the visceral hump, the extent of which is indicated in fig . 38, C, but may be better understood by a glance at the figures of the allied genus See also:

• UMBRELLA

Umbrella (fig . 40), in which the margin of the mantle-skirt coincides, just as it does in the limpet, with the margin of the shell . But in Aplysia the mantle is reflected over the edge of the shell, and grows over its upper surface so as to completely enclose it, excepting at the small central area s where the naked shell is exposed . This enclosure of the shell is a permanent development of the arrangement seen in many Streptoneura (e.g . Pyrula, Ovula, see See also:

• FIGS

figs . 18 and 32), where the border of the mantle can be, and usually is, drawn over the shell, though it is withdrawn (as it cannot be in Aplysia) when they are irritated . From the fact that Aplysia commences its life as a free-swimming veliger with a nautiloid shell not enclosed in any way by the border of the mantle, it is clear that the enclosure of the shell in the adult is a secondary process .

Accordingly, the shell of Aplysia must not be confounded with a primitive shell in its shell-sac, such as we find realized in the shells of See also:

• CHITON

Chiton and in the plugs which form in the remarkable transitory " shell-sac " or " shell-gland " of Molluscan embryos (see figs . 26, 6o) . Aplysia, like other Mollusca, develops a primitive shell-sac in its trochosphere stage of development, which disappears and is succeeded by a nautiloid shell (fig . 36) . This forms the nucleus of the adult shell, and, as the animal grows, becomes enclosed by a reflection of the mantle-skirt . When the shell of an A plysia enclosed in its mantle is pushed well to the left, the sub-pallial space is fully exposed as in fig . 39, and the various apertures of the body are seen . A 9' a, Mouth . b, Radular sac . c, Oesophagus . d, Stomach . c', Intestine .

f', Anus . g, g', g'', gm, The four lobes of the liver . h, The heart (auricle and ventricle) . 1, The renal sac (nephridium) . 1', The ciliated communication of the renal sac with the pericardium . m, The external opening of the renal sac . n, The cerebral ganglion . o, The cephalic tentacles . f, The genital See also:

• PORE

pore . y, The ovo-testes . w, The parasitic hydromedusa Mnestra, usually found attached in this position by the aboral See also:

• POLE (FAMILY)
• POLE, REGINALD (1500-1558)
• POLE, RICHARD DE LA (d. 1525)
• POLE, WILLIAM (1814—1900)

pole of its umbrella . Posteriorly we have the anus, in front of this the lobate gill-plume, between the two (hence corresponding in position to that of the Pectinibranchia) we have the aperture of the renal organ .

In front, near the anterior attachment of the gill-plume, is the osphradium (olfactory organ) discovered by J . W . Spengel, yellowish in See also:

• COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour, in the typical position, and overlying an olfactory ganglion with typical nerve-connexion (see fig . 43) . To the right of Spengel's osphradium is the opening of a peculiar gland which has, when dissected out, the form of ,,, a bunch of grapes; its secretion is said to be poisonous . On the under side of the free edge of the mantle are situated the numerous small cutaneous glands which, in the large A plysia camelus (not in other species), form the See also:

• PURPLE

purple secretion which was known to the ancients . In front away from the See also:

• MID

mid-line . (Lankester.) the aperture of the com- a, Anterior cephalic tentacle. mon or hermaphrodite b, Posterior cephalic tentacle; between a duct . From this point and b, the eyes. there passes forward to , Right epipodium. the right side of the c head a groove—the spermatic groove—down which the spermatic fluid passes . In other Euthyneura this groove may close up and form a canal . At its termination by the side of the head is the See also:

• MUSCULAR

muscular introverted penis . In the hinder part of the foot (See also:

• RIOT (0. Fr. riote, of uncertain etymology)

riot shown in any of the diagrams) is the opening of a large mucus-forming gland very often found in the Molluscan foot .

With regard to internal organization we may commence with the disposition of the renal organ (nephridium), the external opening of which has already been noted . The position of this opening and other features of the renal organ were determined by J . T . See also:

• CUNNINGHAM, ALEXANDER (c.1655-173o)
• CUNNINGHAM, ALLAN (1784-1842)
• CUNNINGHAM, WILLIAM (1805-1861)

Cunningham . There is considerable uncertainty with respect to the names of the species of Aplysia . There are two forms which are very common in the Gulf of See also:

• NAPLES
• NAPLES (Ital. Napoli, and Lat. Neapolis)
• NAPLES, KINGDOM OF

Naples . One is quite See also:

• BLACK
• BLACK, ADAM (1784-1874)
• BLACK, JEREMIAH SULLIVAN (1810–1883)
• BLACK, WILLIAM (1841-1898)

black in colour, and See also:

• MEASURES

measures when outstretched 8 or 9 in. in length . The other is See also:

• LIGHT

light See also:

• BROWN
• BROWN, CHARLES BROCKDEN (1771-181o)
• BROWN, FORD MADOX (1821-1893)
• BROWN, FRANCIS (1849- )
• BROWN, GEORGE (1818-188o)
• BROWN, HENRY KIRKE (1814-1886)
• BROWN, JACOB (1775–1828)
• BROWN, JOHN (1715–1766)
• BROWN, JOHN (1722-1787)
• BROWN, JOHN (1735–1788)
• BROWN, JOHN (1784–1858)
• BROWN, JOHN (1800-1859)
• BROWN, JOHN (1810—1882)
• BROWN, JOHN GEORGE (1831— )
• BROWN, ROBERT (1773-1858)
• BROWN, SAMUEL MORISON (1817—1856)
• BROWN, SIR GEORGE (1790-1865)
• BROWN, SIR JOHN (1816-1896)
• BROWN, SIR WILLIAM, BART
• BROWN, THOMAS (1663-1704)
• BROWN, THOMAS (1778-1820)
• BROWN, THOMAS EDWARD (1830-1897)
• BROWN, WILLIAM LAURENCE (1755–1830)

brown and some-what smaller, its length usually not exceeding 7 in . The first is flaccid and sluggish in its movements, and has not much See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power of contraction; its epipodial lobes are enormously developed and extend far forward along the body; it gives out when handled an abundance of purple liquid, which is derived from cutaneous glands situated on the under side of the free edge of the mantle . According to F . Blochmann it is identical with A. camelus of See also:

• CUVIER, GEORGES LEOPOLD CHRETIEN FREDERIC DAGOBERT, BARON (1769-1832)

Cuvier . The other species is A. depilans; it is See also:

• FIRM

firm to the See also:

• TOUCH (derived through Fr. toucher from a common Teutonic and Indo-Germanic root, cf. " tug," " tuck," O. H. Ger. zucchen, to twitch or draw)

touch, and contracts forcibly when irritated; the secretion of the mantle-glands is not abundant, and is milky See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white in See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance .

The kidney has similar relations in both species, and is identical with the organ spoken of by many authors as the triangular gland . Its superficial extent is seen when the folds covering the shell are cut away and the shell removed; the external surface forms a triangle with its base bordering the pericardium, and its apex directed posteriorly and reaching t6 the Iefthand posterior corner of the shell-chamber . The dorsal surface of the kidney extends to the left beyond the shell-chamber beneath the skin in the space between the shell-chamber and the left parapodium . When the animal is turned on its left-See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand side and the mantle-chamber widely opened, the gill being turned over to the left, a part of the kidney is seen beneath the skin between' the attachment of the gill and the right parapodium (fig . 39) . On examination this is found to be the under surface of the posterior See also:

• LIMB

limb of the gland, the upper surface of which has just been described as lying beneath the shell . In the posterior third of this portion, close tc that edge which is adjacent to the base of the gill, is the external opening (fig . 39, o) . When the pericardium is cut open from above in an animal otherwise entire, the anterior See also:

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

face of the kidney is seen forming. the posterior wall of the pericardial chamber; on the deep edge of this face, a little to the left of the attachment of the auricle to the See also:

• FLOOR (from O. Eng. flor, a word common to many Teutonic languages, cf. Dutch vloer, and Ger. Flur, a field, in the feminine, and a floor, masculine)

floor of the pericardium, is seen a depression ; this depression contains the opening from the pericardium into the kidney . To See also:

• COMPLETE

complete the account of the relations of the organ: the right anterior corner can be seen superficially in the wall of the mantle-chamber above the gill . Thus the base of the gill passes in a slanting direction across the right-hand side of the kidney, the posterior end being dorsal to the apex of the gland, and the anterior end duct, which very soon becomes miniparous gland into phrodite the hermaphrodite entwined in the spire of a gland—the duct . albuminiparous gland .

The latter opens e, Hermaphrodite duct into the common duct at the point k, (uterine portion). and here also is a small diverticulum of b, Vaginal portion of the the duct f . Passing on, we find not uterine duct. far from the genital pore a glandular c, Spermatheca. spherical body (the spermatheca c) open- d, Its duct, See also:

• ING

ing by means of a longish duct into a, Genital pore. the common duct, and then we reach the pore (fig . 39, k) . Here the female apparatus terminates . But when the male secretion of the ovo-testis is active, the seminal fluid passes from the genital pore along the spermatic groove (fig . 39) to the penis, and is by the aid of that eversible muscular organ introduced into the genital pore of a second Aplysia, whence it passes into the spermatheca, there to await the activity of the female See also:

• ELEMENT (Lat. elementum)

element of the ovo-testis of this second Aplysia . After an See also:

• INTERVAL

interval d, Left epipodium . e, Hinder part of visceral hump . fp, Posterior extremity of the foot . fa, Anterior part of the foot underlying the head . g, The ctenidium (branchial plume) . h, The mantle-skirt tightly spread over the horny shell and pushed with it towards the left side .

i, The spermatic groove . k, The common genital pore (male and female) . 1, Orifice of the See also:

• GRAPE

grape-shaped (supposed poisonous) gland . m, The osphradium (olfactory organ of Spengel) . n, Outline of part of the renal sac (nephridium) below the surface . o, External aperture of the nephridium . p, Anus . ventral to the right-hand corner . As so great a part of the whole surface of the kidney lies adjacent to external surfaces of the body, the remaining part which faces the internal organs is small; it consists of the left part of the under surface; it is level with the floor of the pericardium, and lies over the globular mass formed by the liver and convoluted intestine . Thus the renal organ of Aplysia is shown to conform to the Molluscan type . The heart lying within the adjacent pericardium has the usual form, a single auricle and ventricle . The vascular system is not ° rl extensive, the See also:

• ARTERIES (Gr. ap-rnpia, probably from a"spew, to raise, but popularly connected by the ancients with ai7P, air)

arteries soon ending in the well-marked spongy See also:

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

tissue which builds up the muscular foot, parapodia, and dorsal body-wall .

The alimentary canal commences with the usual buccal mass; the lips are cartilaginous, but not armed with horny jaws, though these are common in other Opisthobranchs; the lingual ribbon is multidenticulate, and a pair of salivary glands pour in their secretion . The oesophagus expands into a curious gizzard, which is armed internally with large horny processes, some broad and thick, others spinous, fitted to See also:

• ACT (Lat. actus, actum)

act as crushing See also:

• INSTRUMENTS

instruments . From this we pass to a stomach and a coil of intestine embedded in the lobes of a voluminous liver; a caecum of large size is given off near the commencement of the intestine . The liver opens by two ducts into the digestive FIG . 4i—Gonad, and See also:

• TRACT (from Lat. tractare, to treat of a matter, through Provencal tractat and Ital. trattato)

tract. accessory glands and The generative organs See also:

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

lie close to the ducts of Aplysia . (Lan-coil of intestine and liver, a little to the kester.) left side . When dissected out they ap- Ovo-testis, See also:

• PEAR (Pyrus communis)

pear as represented in fig . 41 . The h, Hermaphrodite duct. essential reproductive organ or gonad g, Albuminiparous gland. consists of both ovarian and testicular f Vesicula seminalis. cells (see fig . 42) . It is an ovo-testis. k, Opening of the albu-From it passes a common or herma- of some days—possibly See also:

• WEEKS, EDWIN LORD (1849-1903)

weeks—the ova of the second Aplysia commence to descend the hermaphrodite duct; they become en- A 1 closed in a viscid secretion at the point where the albuminiparous gland opens into the duct intertwined with it; and on reaching the point where the spermathecal duct debouches they are impregnated by the spermatozoa which 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 now from the spermatheca and meet the ova . The development of Aplysia from the egg presents many points of See also:

• INTEREST

interest from the point of view of comparative embryology, but in relation to the See also:

• MORPHOLOGY, (Gr. yopdsil, form)

morphology of the Opisthobranchia it is sufficient to point to the occurrence of a trochosphere and a veliger stage (fig .

36), and of a shell-gland or primitive shell-sac (fig . 36, shgr), which is succeeded by a nautiloid shell . In the nervous system of Aplysia the great ganglion-pairs are well developed and distinct . The euthyneurous visceral loop is long, and presents only one ganglion (in Aplysia camelus, but two distinct ganglia joined to one another in Aplysia hybrida' of the English coast), placed at its extreme limit, representing both the right and left visceral ganglia and the third or abdominal ganglion, which are so often separately present . The See also:

• DIAGRAM

diagram (fig . 43) shows the nerve connecting this abdomino-visceral ganglion with the olfactory ganglion of Spengel . It is also seen to be connected with a more remote ganglion—the genital . Such special irregularities in the develop- ment of ganglia upon the visceral loop, and on one or more of the See also:

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

main nerves connected with it, are very frequent . Our figure of the nervous system of Aplysia does not give the small pair of buccal ganglia which are, as in all glossophorous Molluscs, present upon the nerves passing from the cerebral region to the odontophore . For a comparison of various Opisthobranchs, Aplysia will be found to present a convenient starting-point . It is one of the more typical Opisthobranchs, that is to say, it belongs to the section Tectibranchia, but other members of the sub-order, namely, Bulla and Actaeon (figs . 44 and 45), are less abnormal than Aplysia in regard to their shells and the form of the visceral hump .

They have naked spirally twisted shells which may be concealed from view in the living animal by the expansion and reflection of the parapodia, but are not enclosed by the mantle, whilst Actaeon is remarkable for possessing an operculum like that of so many Streptoneura . The great development of the parapodia seen in Aplysia is usual in Tectibranchiate Opisthobranchs . The whole surface of the body becomes greatly modified in those Nudibranchiate forms which have lost, not' only the shell, but also the ctenidium . Many of these have peculiar processes developed on the dorsal surface (fig . 46, A, B), or retain purely negative characters (fig . 46, D) . The See also:

• CHIEF (from Fr. chef, head, Lat. caput)

chief modification of internal organization presented by these forms, as compared with Aplysia, is found in the condition of the alimentary canal . The liver Is no longer a compact organ opening by a pair of ducts into the median digestive tract, but we find very numerous hepatic diverticula on a shortened axial tract (fig . 47) . These diverticula extend usually one into each of the dorsal papillae or " cerata " when these are present . They are not merely digestive glands, but are sufficiently wide to act as receptacles 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, and in them the digestion of food proceeds just as in the axial portion of the canal . A precisely similar modification of the liver or great digestive gland is found in the scorpions, where the axial portion of the digestive canal is short and straight, and the lateral ducts sufficiently wide to admit food into the ramifications of the gland there to be digested; whilst in the See also:

• SPIDERS

spiders the gland is reduced to a series of simple caeca .

The typical character is retained by the heart, pericardium, and the communicating nephridium or renal organ in all Opisthobranchs . An interesting example of this is furnished by the See also:

• FISH (O. Eng. fist, a word common to Teutonic languages, cf. Dutch visch, Ger. Fisch, Goth. fisks, cognate with the Lat. piscis)
• FISH, HAMILTON (1808-1893)

fish-like trans-See also:

• PARENT, SIMON NAPOLEON (1855– )

parent Phyllirhoe (fig . 37), in which it is possible most satisfactorily to study in the living animal, by means of the See also:

• MICROSCOPE (Gr. µucp6s, small, asenreiv, to %view)

microscope, the course of the See also:

• BLOOD

blood-stream, and also the See also:

• RENO

reno-pericardial communication . In many of the Nudibranchiate Opisthobranchs the nervous system presents a concentration of the ganglia (fig . 48), contrasting greatly with what we have seen in Aplysia . Not only are the pleural ganglia fused to the cerebral, but also the visceral to these (see in further See also:

• ILLUSTRATION

illustration the condition attained by the Pulmonate Limnaeus, fig . 59), and the visceral loop is astonishingly short and insignificant (fig . 48, e') . That the parts are rightly thus identified is probable from J . W . Spengel's observation of the osphradium and its nerve-supply in these forms; the nerve to that organ, which is placed somewhat anteriorly—on the dorsal surface—being given off from the hinder part (visceral) of the right See also:

• COMPOUN