Coral and Coral Reefs.docx

Coral and Coral Reefs.docx

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CoralandCoralReefs

CoralandCoralReefsbyThomasH.HuxleyTHEsubjectuponwhichIwishtoaddressyouto-nightisthestructureandoriginofCoralandCoralReefs.Undertheheadof"coral"thereareincludedtwoverydifferentthings;oneofthemisthatsubstancewhichIimagineagreatnumberofushavechampedwhenwewereverymuchyoungerthanwearenow,--thecommonredcoral,whichisusedsomuch,asyouknow,fortheedificationandthedelectationofchildrenoftenderyears,andisalsoemployedforthepurposesofornamentforthosewhoaremucholder,andassomethinkmightknowbetter.Theotherkindofcoralisaverydifferentsubstance;itmayfordistinction'ssakebecalledthewhitecoral;itisamaterialwhichmostassuredlynotthehardest-heartedofbabyfarmerswouldgivetoababytochew,anditisasubstancewhichistobeseenonlyinthecabinetsofcuriouspersons,orinmuseums,or,maybe,overthemantelpiecesofsea-faringmen.Butalthoughtheredcoral,asIhavementionedtoyou,hasaccesstotheverybestsociety;andalthoughthewhitecoraliscomparativelyadespisedproduct,yetinthis,asinmanyothercases,thehumblerthingisinrealitythegreater;theamountofworkwhichisdoneintheworldbythewhitecoralbeingabsolutelyinfinitecomparedwiththateffectedbyitsdelicateandpamperednamesake.Eachofthesesubstances,thewhitecoralandthered,however,hasarelationshiptotheother.Theyare,inazoologicalsense,cousins,eachofthembeingformedbythesamekindofanimalsinwhatissubstantiallythesameway.Eachofthesebodiesis,infact,thehardskeletonofaverycuriousandaverysimpleanimal,morecomparabletothebonesofsuchanimalsasourselvesthantotheshellsofoystersorcreaturesofthatkind;foritisthehardeningoftheinternaltissueofthecreature,ofitsinternalsubstance,bythedepositinthebodyofamaterialwhichisexceedinglycommon,notonlyinfreshbutinseawater,andwhichisspeciallyabundantinthosewaterswhichweknowas"hard,"thosewaters,forexample,whichleavea"fur"uponthebottomofatea-kettle.This"fur"iscarbonateoflime,thesamesortofsubstanceaslimestoneandchalk.Thatmaterialiscontainedinsolutioninseawater,anditisoutoftheseawaterinwhichthesecoralcreatureslivethattheygetthelimewhichisneededfortheformingoftheirhardskeleton.

Butnowwhatmannerofcreaturesarethesewhichformthesehardskeletons?

Idaresaythatinthesedaysofkeepingaquaria,oflocomotiontothesea-side,mostofthosewhomIamaddressingmayhaveseenoneofthosecreatureswhichusedtobeknownasthe"seaanemone,"receivingthatnameonaccountofitsgeneralresemblance,inaroughsortofway,totheflowerwhichisknownasthe"anemone";butbeingathingwhichlivesinthesea,itwasqualifiedasthe"seaanemone."Well,then,youmustsupposeabodyshapedlikeashortcylinder,thetopcutoff,andinthetopaholeratherovalthanround.

Allroundthisaperture,whichisthemouth,imaginethatthereareplacedanumberoffeelersformingacircle.Thecavityofthemouthleadsintoasortofstomach,whichisveryunlikethoseofthehigheranimals,inthecircumstancethatitopensatthelowerendintoacavityofthebody,andallthedigestedmatter,convertedintonourishment,isthusdistributedthroughtherestofthebody.Thatisthegeneralstructureofoneoftheseseaanemones.Ifyoutouchititcontractsimmediatelyintoaheap.Itlooksatfirstquitelikeaflowerinthesea,butifyoutouchityoufindthatitexhibitsallthepeculiaritiesofalivinganimal;andifanythingwhichcanserveasitspreycomesnearitstentacles,itclosesthemrounditandsucksthematerialintoitsstomachandtheredigestsitandturnsittotheaccountofitsownbody.

Thesecreaturesareveryvoracious,andnotatallparticularwhattheyseize;andsometimesitmaybethattheylayholdofashellfishwhichisfartoobigtobepackedintothatinteriorcavity,and,ofcourse,inanyordinaryanimalaproceedingofthiskindwouldgiverisetoaveryseverefitofindigestion.Butthisisbynomeansthecaseintheseaanemone,becausewhendigestivedifficultiesofthiskindarisehegetsoutofthembysplittinghimselfintwo;andtheneachhalfbuildsitselfupintoafreshcreature,andyouhavetwopolypeswheretherewaspreviouslyone,andthebonewhichstuckinthewaylyingbetweenthem!

Notonlycanthesecreaturesmultiplyinthisfashion,buttheycanmultiplybybuds.Abudwillgrowoutofthesideofthebody（I

amnotspeakingofthecommonseaanemone,butofalliedcreatures）

justlikethebudofaplant,andthatwillfashionitselfintoacreaturejustliketheparent.Therearesomeoftheminwhichthesebudsremainconnectedtogether,andyouwillsoonseewhatwouldbetheresultofthat.IfImakeabudgrowouthere,andanotherontheoppositeside,andeachfashionsitselfintoanewpolype,thepracticaleffectwillbethatbeforelongyouwillseeasinglepolypeconvertedintoasortoftreeorbushofpolypes.Andthesewillallremainassociatedtogether,likeakindofco-operativestore,whichisathingIbelieveyouunderstandverywellhere,--eachmouthwillhelptofeedthebodyandeachpartofthebodyhelptosupportthemultifariousmouths.Ithinkthatisasgoodanexampleofazoologicalco-operativestoreasyoucanwellhave.Sucharethesewonderfulcreatures.Buttheyarecapablenotonlyofmultiplyinginthisway,butinotherways,byhavingamoreordinaryandregularkindofoffspring.Littleeggsarehatchedandtheyoungarepassedoutbythewayofthemouth,andtheygoswimmingaboutaslittleovalbodiescoveredwithaverycuriouskindofhairlikeprocesses.Eachoftheseprocessesiscapableofstrikingwaterlikeanoar;andtheconsequenceisthattheyoungcreatureispropelledthroughthewater.Sothatyouhavetheyoungpolypefloatingaboutinthisfashion,coveredbyits'vibratilecilia',astheselongfilaments,whicharecapableofvibrationaretermed.Andthus,althoughthepolypeitselfmaybeafixedcreatureunabletomoveabout,itisabletospreaditsoffspringovergreatareas.Forthesecreaturesnotonlypropelthemselves,butwhileswimmingaboutintheseaformanyhours,orperhapsdays,itwillbeobviousthattheymustbecarriedhitherandthitherbythecurrentsofthesea,whichnotunfrequentlymoveattherateofoneortwomilesanhour.Thus,inthecourseofafewdays,theoffspringofthisstationarycreaturemaybecarriedtoaverygreatdistancefromitsparent;andhavingbeensocarrieditlosestheseorgansbywhichitispropelled,andsettlesdownuponthebottomoftheseaandgrowsupagainintotheformandconditionofitsparents.Sothatifyousupposeasinglepolypeofthiskindsettleduponthebottomofthesea,itmaybythesevariousmethods--thatistosay,bycuttingitselfintwo,whichwecall"fission,"orbybudding;orbysendingouttheseswimmingembryos,--multiplyitselftoanenormousextent,andgiverisetothousands,ormillions,ofprogenyinacomparativelyshorttime;

andthesethousands,ormillions,ofprogenymaycoveraverylargesurfaceoftheseabottom;infact,youwillreadilyperceivethat,givethemtime,andthereisnolimittothesurfacewhichtheymaycover.

Havingunderstoodthusfarthegeneralnatureofthesepolypes,whicharethefabricatorsbothoftheredandwhitecoral,letusconsideralittlemoreparticularlyhowtheskeletonsoftheredcoralandofthewhitecoralareformed.Theredcoralpolypeperchesupontheseabottom,itthengrowsupintoasortofstem,andoutofthatstemtheregrowbranches,eachofwhichhasitsownpolypes;andthusyouhaveakindoftreeformed,everybranchofthetreeterminatedbyitspolype.Itisatree,butattheendofthebranchesthereareopenmouthsofpolypesinsteadofflowers.Thusthereisacommonsoftbodyconnectingthewhole,andasitgrowsupthesoftbodydepositsinitsinterioraquantityofcarbonateoflime,whichacquiresabeautifulredorfleshcolour,andformsakindofstemrunningthroughthewhole,anditisthatstemwhichistheredcoral.TheredcoralgrowsprincipallyatthebottomoftheMediterraneanSea,atverygreatdepths,andthecoralfishers,whoareveryadventurousseamen,taketheirdragnets,ofapeculiarkind,roughlymade,butefficientfortheirpurpose,anddragthemalongthebottomoftheseatocatchthebranchesoftheredcoral,whichbecomeentangledandarethusbroughtuptothesurface.Theyarethenallowedtoputrefy,inordertogetridoftheanimalmatter,andtheredcoralistheskeletonthatisleft.

Inthecaseofthewhitecoral,theskeletonismorecomplete.Intheredcoral,theskeletonbelongstothewhole;inthewhitecoralthereisaspecialskeletonforeveryoneofthesepolypesinadditiontothatforthewholebody.Thereisaskeletonformedinthebodyofeachofthem,likeacupdividedbyanumberofradiatingpartitionstowardstheoutside;andthatcupisformedofcarbonateoflime,onlynotstainedred,asinthecaseoftheredcoral.Andallthesecupsarejoinedtogetherintoacommonbranch,theresultofwhichistheformationofabeautifulcoraltree.Thisisagreatmassofmadrepore,andinthelivingstateeveryoneoftheendsofthesebrancheswasterminatedbyabeautifullittlepolype,likeaseaanemone,andalltheskeletonwascoveredbyasoftbodywhichunitedthepolypestogether.Youmustunderstandthatallthisskeletonhasbeenformedintheinteriorofthebody,tosuitthebranchedbodyofthepolypemass,andthatitisasmuchitsskeletonasourownbonesareourskeleton.Inthisnext