mollusc

See mollusk. Mollusca (mo-lus'kä), n. pl. [NL., pl. of mol luscum, a soft-bodied animal, a mollusk: see mollusk.] One of the leading divisions of in vertebrated animals; an extensive series of invertebrates whose bodies are soft, without any jointed legs, and commonly covered with a hard Mollusca shell in one, two, or more pieces, and whose principal parts are neither segmented into a series of longitudinal rings, as in insects, crustaceans, and worms, nor radiately arranged, as in echinoderms; the mollusks, as the univalve or bivalve shell-fish of ordinary language. Mollusks have no trace of a notochord or urochord, which distinguishes them from certain organisms, as ascidians, formerly cla ed with them. They are primitively bilaterally symmetrical, or have a right and left "side" along a main axis; this form is best expre ed in the chitons, and is evident in bivalves, slugs, etc., but its expre ion is often obscured by a twisting to which the body is subjected in various univalves, as those whose shells are spiral. (See I so pleura, An i so pleura.) There is always a well-defined alimentary canal, with definite walls. A nervous system is well developed as a set of ganglia with connecting commi ures, one characteristic feature of which is the formation of a nervous ring or collar around the gullet, and another is the torsion of the visceral commi ures in those forms whose bodies are twisted as above said. (See Euthyneura, Strep ton eur a.) Most mollusks have a distinct head, which, however, is not apparent in bivalves, leading to a division of headle mollusks ( Acephala or Lipo cephala). A characteristic organ of Glo ophora or mollusks with heads is the odontophore, buccal ma , or lingual ribbon, whose radula serves as a rasping-organ in a mouth otherwise soft and toothle . Various modifications of the radular teeth give rise to several descriptive terms. (See ptenoglo ate, rach i glo ate, rhipidoglo ate, tænioglo ate.) There is always a heart, with a ventricle and at least one auricle, and dorsal in position. Its relative situation with respect to the gills differs in certain groups of mollusks. (See opisthobranch i ate, proso branchiate.) The circulation is double. The respiratory system is branchial, and in some cases, as of snails and slugs, modified for breathing air into a kind of lung. (See Pulmonata, Gasteropod a.) The primitive typical gills are paired organs called ctenidia; but undergo many modifications, and their function respiration may be a umed vicariously by other parts of the body not homologous with them. These modifications give rise to the names of many subordinate groups of mollusks, especially of gastropods, besides that of the great series Lamellibranch i at a. The renal organs of mollusks are technically called nephridia, or organs of Bojanus. (See cut under Lamellibranch i at a.) The sexual organs are developed, either in the same individuals, or in different individuals of opposite sexes. The characteristic organ of locomotion is the foot or podium, a development of the under surface of the body, which may be a broad flat sole (see cut under Gasteropod a ), upon which the mollusk creeps, or otherwise shaped. It is often wanting, as in the oyster, or may give rise to a thready by us by which the animal is rooted, as in the mu el. Forms of the podium give names to most of the leading groups of mollusks, as cephalopods, pteropods, scaphopods, heteropods, gastropods, and pelecy pods. A large part of the soft integument of mollusks forms what is called the mantle or pallium, from which the shell, when present, is developed (see integropalliate, sinupalliate ), and the impre ion of the edge of the mantle on the inside of the shell is the pallial line. Some mollusks are entirely naked, or have only a rudimentary and concealed shell, as land-slugs and sea-slugs, and also most of the living cephalopods. The body of cephalopods is strengthened by an internal skeleton, the calamary or cuttlebone, though no mollusk has an articulated internal skeleton. But the great majority of mollusks have a hard shell (whence the old names Testacea, Ostracoderm at a), of a horny or chitinous or more decidedly calcareous substance. whose shell are called univalves; those in; but which it forms a hinged pair of shells are bivalves, the former may have an additional shelly piece, closing the aperture, the operculum; and the two main valves of the latter may be supplemented by acce ory valves (see cut under acce ory). Bivalves are the natural group of headle or lamellibranch mollusks; but univalves include several orders, though the word is chiefly used of the numerous and conspicuous gastropods. A few mollusks are technically multi valve; such are the chitons, hence called Polyplacophora, having several segments of the shell in lengthwise series. (See cut under chiton.) Cirripeds used to be considered multi valve mollusks. The shell is usually covered outside with a rough skin or epidermis; inside it may be beautifully lustrous, as with mother-of-pearl. Most mollusks live either in salt, brackish, or fresh water; land mollusks are mostly found in damp places. Most are locomotory, either by creeping or by swimming; some swim by flapping their shells, others by moving various appendages; many adhere to or even burrow deeply in rocks; a few are parasitic. Some are carnivorous, others herbivorous; most are oviparous, a few ovoviviparous. Many are important as food, and the shells of many are put to useful or ornamental purposes. Certain bivalves furnish pearls. The Mollusca have been variously rated, limited, and cla ified; at one time the bodies of the animals were differently named from their shells. (See Limax.) (1) The name was originally proposed by Jonston in 1650 for naked cephalopods and for Aplysia, and adopted by Linnæus in 1758 as his second order of Vermes, including similar naked forms and some heterogeneous elements. Linnæus made the Testacea or shelled mollusks his third order of Vermes; and these two groups were combined as a cla by Poli in 1791. (2) About 1800 Cuvier made Mollusca the second of his four branches of the animal kingdom, with seven cla es, Cephalopod a, Gasteropod a, Pteropod a, Acephala, Brachiopod a, Nuda, and Cirrhopoda (the Nuda being ascidians, and the Cirrhopoda being crustaceans). (3) In Lamarck's system, 1819, Mollusca, as a cla , were exclusive of the bivalves (called by him Con chifera ), and were divided into five orders, Pteropod a, Gas teropoda, Trachelipoda, Cephalopod a, and Heteropod a. (4) In 1839 Swains on extended Mollusca to all invertebrates except the articulates. (5) The cirripeds having been recognized as crustaceans by Thompson in 1830, and the same naturalist having at the same time investigated the polyzoans, the relation of the latter to the brachiopods led H. Milne-Edwards in 1844 to a ociate the two Cuvierian groups Brachiopod a and Nuda with the Polyzoa in a division called Molluscoidea (the vertebrate affinities of the Nuda or ascidians not being recognized till much later, in 1866). (6) These di ociations from Mollusca in a former IMG:content-0850.png:[blocks in formation] taining the ova or embryos of the molluscan molochine (mol'ō-kin), a . and n. I. a. Of or parasite Entoconcha mirabilis . moll-washer (mol'wosh"èr), n. The washer or wagtail, a bird. Also called molly wash - dish , etc. [Local, Eng.] moll-wire (mol' wir), n. A pickpocket who robs women only. [Thieves' slang.] Molly1 (mol'i), n. [Dim. of Moll , or var. of the orig. Mary : see Molll .] 1. A familiar form of the feminine name Mary . -2. [l.c.; pl. mollies (-iz).] The wagtail, a bird: as, the yellow molly (the yellow wagtail); the molly wash-dish (the pied wagtail). [Local, Eng.] molly2 (mol'i), n.; pl. mollies (-iz). [Abbr. of mollymawk, mallemuck .] The mallemuck or fulmar, Fulmar us glacial is . See fulmar2 . molly3 (mol'i), n.; pl. mollies (-iz). [Hind. mali.] In India, a gardener or one of the caste of gar- deners. Also mallee . Molochize (mõʻlok-iz), v . t .; pret. and pp. Mo- lochized , ppr. Molochizing . [ Moloch + -ize .] To sacrifice or immolate as to Moloch. [Rare.] I think that they would Molochize them [their babies] too, To have the heavens clear. Tennyson, Harold, i. 1. moloid (mol'oid), a . and n. I. a. Of or per- taining to the Moloidea . molly cottontail. See cottontail. Molly Maguire (mol'i ma-gwir'). [A name as- sumed (from Molly , a familiar form of the fem i- nine name Mary , and Maguire , a common Irish surname) by the members of the organization (def. 1), in allusion to the woman's dre they sus.] Same as molo us , 1. molopes (mộ-lō'pēz), n. pl . [NL., pathol ., same as vibices . named Molly Maguire .] 1. A member of a law- le secret a ociation in Ireland, organized with the object of defeating and terrorizing agents and proce -servers, and others engaged proce -servers, and either duck them in bog-holes or Molly Maguires became the terror of all our officials. beat them in the most unmerciful manner, so that the Hence-2. A member of a secret organization in the mining regions of Pennsylvania, no to- rio us for the commi ion of various crimes, including murderous attacks upon the owners, officers, or agents of mines, until their sup- pre ion by the execution of several of their leaders, about 1877. mollymawk (mol'i-mak), п. mallemuck . molly-pufft (mol'i-puf), n. A gambling decoy. Thou molly - puff ! were it not justice to kick thy guts out? Shirley, The Wedding, iv. 3. Moloch (mōʻlok), n. [Also sometimes Molech ; Moloch , mōlekh (usually with the article) (also Milkōm , Malkām , > Gr. Μελχόμ, Ε. Milcom ); cf. melekh (= Ar. melik , king, mālakh , reign, part. mõlēkh , reign- ing).] 1. The chief god of the Phenic i ans, fre- quently mentioned in Scripture as the god of the Ammonites, whose worship consisted chiefly of human sacrifices, ordeals by fire, mutilation, etc.: also identified with the god of the Cartha- ginians called by cla ical writers Kronos or Saturn. Hence the word has now become a designation of any baneful influence to which everything is sacrificed. And they built the high places of Baal, to cause their sons and their daughters to pa through the fire unto Molech ; which I commanded them not. First Moloch , horrid king, besmear'd with blood Of human sacrifice, and parents' tears. Milton , P. L., i. 392. It was a very Moloch of a baby, on whose insatiate altar the whole existence of this particular young brother was offered up a daily sacrifice. Dickens , The Haunted Man, ii. 2. [NL.] The typical genus of Moloch inæ . There is but one species, M. horrid us of Australia, one of the most repulsive, though in reality one of the most harm- le , of reptiles, the horns on the head and the numerous spines on the body giving it a formidable aspect. Moloch inæ (mol-ō-kīnē), n . pl . [NL., Moloch +-inæ.] A subfamily of agamoid lizards hav- ing a depre ed body, a very small mouth, and the upper teeth directed horizontally inward. The body is beset with large spines, especially on the head, giving an ugly and formidable appearance to an entirely harmle creature. IMG:content-0851.png:[blocks in formation] To make ony myrthe ffor mowtynge that nyghed. Richard the Redele , ii. 12. molto (mol'tō), adv . [It., very much, multitude .] In music, very; much: as, allegro molto , very fast. Molucca bean, deer, etc. See bean , etc. Moluccella (mol-uk-sel'ä), n. [NL. (Linnæus, 1737), named from the Molucca Islands, of which the plant was supposed to be a native.] A genus of labiate plants of the tribe Stachy- IMG:content-0852.png:[blocks in formation] at the apex, with an oblique limb having from to teen unequal spiny teeth, and by having the anther-cells extremely divergent. They are very smooth annual herbs, with petiolate leaves and axillary whorls of small flowers. There are but 2 species, both native in the eastern Medi- terrane an region. M. lævis , an old garden-flower from Asia, once supposed to come from the Moluccas, is called Moluc- ca balm , and also shell - flower , from its large cup-shaped calyx, which has the small corolla at the bottom. Molva (mol'vä), n. [NL. (Nil on, 1832), a name of this fish.] A genus of gadoid fishes, related to the burbots and cusks, having the mouth terminal, anal fin entire, and canine teeth on molybdosis (mol-ib-dō'sis), n. [NL., M. molva or vulgar is is the common ling of North Atlantic waters. See cut under ling . molwartt, n. See moldwarp . molyl (mo'li), a . [Also moley ; mole2 + -y1.] Like a mole or its habits. [Rare.] He... did... infinite service in discouraging the moley , creeping style, which at that time infected all the ranks both of the laity and clergy. IMG:content-0853.png:[blocks in formation] molten1 (mol'tn), p . a. [Pp. of melt1 .] 1. Melt- ed; in a state of fusion or solution: as, molten gold. Love's my stick form the artizans of Greece In wounded stone or molten gold expre . Prior. Solid iron floats upon molten iron exactly as ice floats Tyndall , Forms of Water, p. 124. A prince whose manhood was all gone, And molten down in mere uxoriousne . Goldsmith, Encouragers and Discouragers of English [Literature, ii. moly2 (mo'li), n. [L. moly, μῶλυ , a fabu- lous herb.] 1. A fabulous herb of magic pow- er, represent represented as having a black root and the flower milk-white, said by Homer to have been given by Hermes to Ody eus (Uly es) to coun- teract the spells of Circe. And yet more med'cinal is it than that moly That Hermes once to wise Uly es gave. But as ye hearb moly hath a floure as white as snow, and a roote as blacke as incke, so age hath a white head, showing pietie, but a black hart, swelling with mischiefe. Lyly, Euphues and his England (Arber's Reprints, IV. 231). Homer is of opinion That the principall and soveraigne hearb of all others is moly ; so called (as he think eth) by the Gods themselves. Holland, tr. of Pliny, xxv. 4. 2. Wild garlic, Allium Moly . The moly of Dios- corides is said to have been Allium subhirsutum ; the dwarf moly is A. Chamæmoly . molybdate (mo-lib'dāt), n. [ molybd ( ic ) + -atel.] A compound of molybdic acid with a base.-Molybdate of lead, yellow lead ore; the min- eral wulfenite. See wulfenite . molybdena (mol-ib-dē'nä), n. [F. molybdène = Sp. It. molibdena = Pg. molybdene , molybdena , molybdæna , μολύβδαινα , galena or lith- arge, μόλυβδος , lead, = L. plumbum , lead: see plumb .] Same as molybdenum . momblementt, n. See mumblement . momblishne (mom'blish-nes), n. Muttering talk. Bailey , 1731. momel (mom), n. [ I dare be bold awhile to play the mome , Out of my sacke some other faults to lease. Mome , malt-horse, capon, coxcomb, idiot, patch! Shak., C. of E., iii. 1. 32. Words are but wind, but blowes come home, A stout tongu'd lawyer 's but a mome. Brome's Songs (1661), p. 105. ( Hall i well .) Parna us is not clome molybdeniferous (molib-de-nif'e-rus), a . L. molybdæna (see molybdena ) + ferre = E. bear1.] Containing molybdenum. molybdenite (mol-ib-dēnīt), n. [ molybdena +-ite2.] Sulphid of molybdenum, occurring in foliated ma es or in scales, le often in hex- agonal crystals, of a lead-gray color and metallic luster. It is very soft, and, like graphite, which it closely resembles, leaves a trace on paper. And he received them at their hand, and fashioned it molybdenous (mol-ib-dē'nus), a. [ num + -ous.] Pertaining to or obtained from molybdenum. molybdenum (mol-ib-dē'num), n. [ molyb- dænum , a later form for L. molybdœna : see molyb- den a.] Chemical symbol, Mo; atomic weight, 95.8. A metal of a silver-white color, but hard- er than silver, which fuses with difficulty, if at all, at the highest temperature of a wind-fur- nace. Its specific gravity is 8.6. It is chemically re- lated to chromium, tungsten, and uranium, and, like those metals, forms trioxids which are acid-forming and yield very characteristic salts. It is remarkable for the number of oxids and corresponding chlorids which it forms; but it is the least important economically of the group to which it belongs. The most abundant ore of molybdenum is the sulphuret (molybdenite), and the strong external resemblance of this mineral to graphite (Latin plumbago ) led to the confusion of molybdena with that substance; moreover, external resemblance and certain chemical pe- culiarities caused still further difficulties of nomencla- ture, in which manganese, antimony, and even magnesia were involved. Thus, the peroxid of manganese was called by Linnæus molybdænum magnes i i. These per- plexities were not cleared up until toward the end of the last century; but finally, as the result of the labors Quarles, Emblems, v. 4. of Scheele, Bergman, and Hjelm (1778-90), the metal O hath my leaden soul the art t' improve Her wasted talent, and, unrais'd, aspire In this sad moulting time of her desire? (b) Precise point of time; exact or very instant, as of a motion, action, or occurrence:: as, at that moment he ex- pired. A prince, the moment he is crown'd, Inherits every virtue sound. Swift , On Poetry, 1. 90. Every moment dies a man, Every moment one is born. The "Daily News" expre es the general sense...in recognizing defeat as decisive for the moment . New York Tribune , July 15, 1886. 2. The present time; especially, with the def- inite article, the precise instant of opportunity. The moment should be improved; if suffered to pa away, it may never return. Washington, in Bancroft's Hist. Const., I. 21. The Century Dictionary and Cyclopedia: The Century dictionary IMG:content-0855.png:[blocks in formation] Each on himself relied, As only in his arm the moment lay Of victory. Milton , P. L., vi. 239. 4. Notable purport; weight or value; importance; consequence: as, his opinions are of little moment to us. Being for many respects of greater moment , to haue them princes] good and vertuous then any inferior sort of men. Putten ham , Arte of Eng. Poesie, p. 28. Captall criminals, or matters of moment , before the Chan himselfe, or Priuie Counsells, of whom they are alwayes heard, and speedily discharged. Capt. John Smith , True Travels, I. 36. 51. A forcible or convincing plea. He.. pre ed the former arguments, refuted the cavils,. and added. many moments and weights to his discourse. Jer. Taylor, Works (ed. 1835), II. 77. 6. An e ential or constituent element; an important factor. It is a complete mistake historically to a ume that the moment of Cartes i an ism is consciousne . Veitch , Introd. to Des cartes's Method, p. lxxix. 7. In math., an increment or decrement; an infinitesimal change in a varying quantity.-8. In mech ., in general, effect; avail. The phrases in which it appears have exact meanings, though the precise sense in which the word itself is taken in these phrases is not always clear. -Bending-moment. Same as moment of flexure. Equation of moments. See equation Logical moments. See logical. - Moment-axis of a couple, the line which represents in direction the direction of a couple, and by its length the moment. - Moment of a couple, the product of the force by the length of the arm.-Moment of a force. ( a ) With regard to a point, the product of a force by its distance from the point. (b) With reference to a line or axis, the product of the component of the force in the plane perpendicular to the line by the distance of that component from that line.- Моment of a magnet, or magnetic moment, the product of the numerical strength of either pole of the magnet by the distance between the poles. The total moment of a magnet is the moment when it is at right angles to the lines of force. J. E. H. Gordon , Elect, and Mag., I. 151. Moment of deviation or distortion. Same as product of inertia (which see, under inertia ). - Moment of flexure. See flexure. - Moment of inertia. See inertia. Moment of rupture, the moment of flexure of a beam calculated for a predetermined or a umed breaking load and leverage. Its formula is M = nfbh2 , in which b = breadth, h = depth, na factor varying with shape of cro section, and ƒ a factor depending on the nature of the material. Both factors n and f are determined and tabulated for different materials from experimental data. - Moment of stability of a body or structure supported at a given plane joint, the moment of the couple of forces which must be applied in a given vertical plane to that body or structure in addition to its own weight, in order to transfer the center of resistance of the joint to the limiting position consistent with stability. Rankine. -Virtual moment of a force, the product of the force by the virtual velocity of the point of application. = Syn. 1. Moment , Minute , Instant, twinkling, second, trice, flash. A moment has duration, an instant has not: as, wait a moment ; come this instant. Practically, however, the two are often the same. A minute is just sixty seconds; a moment is a short but le definite period. Moments make the year. Young , Love of Fame, vi. 205. There are minutes that fix the fate Of battles and of nations. H. H. Brownell, The Bay-Fight. The duke does greet you, general, And he requires your haste-post-haste appearance, Even on the instant . Shak., Othello, i. 2. 38.