33
Inthecaseofanimalsthatarequadrupedsandred-bloodedandoviparous，generationtakesplaceinthespring，butcopulationdoesnottakeplaceinanuniformseason。Insomecasesittakesplaceinthespring，inothersinsummertime，andinothersintheautumn，accordingasthesubsequentseasonmaybefavourablefortheyoung。
Thetortoiselayseggswithahardshellandoftwocolourswithin，likebirds'eggs，andafterlayingthemburiestheminthegroundandtreadsthegroundhardoverthem；itthenbroodsovertheeggsonthesurfaceoftheground，andhatchestheeggsthenextyear。
Thehemys，orfresh-watertortoise，leavesthewaterandlaysitseggs。Itdigsaholeofacasklikeshape，anddepositsthereintheeggs；afterratherlessthanthirtydaysitdigstheeggsupagainandhatchesthemwithgreatrapidity，andleadsitsyoungatonceofftothewater。Thesea-turtlelaysonthegroundeggsjustliketheeggsofdomesticatedbirds，buriestheeggsintheground，andbroodsovertheminthenight-time。Itlaysaverygreatnumberofeggs，amountingattimestoonehundred。
Lizardsandcrocodiles，terrestrialandfluvial，layeggsonland。
Theeggsoflizardshatchspontaneouslyonland，forthelizarddoesnotliveonintothenextyear；infact，thelifeoftheanimalissaidnottoexceedsixmonths。Theriver-crocodilelaysanumberofeggs，sixtyatthemost，whiteincolour，andbroodsoverthemforsixtydays:for，bytheway，thecreatureisverylong-lived。Andthedisproportionismoremarkedinthisanimalthaninanyotherbetweenthesmallnessoftheoriginaleggandthehugesizeofthefull-grownanimal。Fortheeggisnotlargerthanthatofthegoose，andtheyoungcrocodileissmall，answeringtotheegginsize，butthefull-grownanimalattainsthelengthoftwenty-sixfeet；infact，itisactuallystatedthattheanimalgoesongrowingtotheendofitsdays。
34
Withregardtoserpentsorsnakes，theviperisexternallyviviparous，havingbeenpreviouslyoviparousinternally。Theegg，aswiththeeggoffishes，isuniformincolourandsoft-skinned。Theyoungserpentgrowsonthesurfaceoftheegg，and，liketheyoungoffishes，hasnoshell-likeenvelopment。Theyoungoftheviperisborninsideamembranethatburstsfromofftheyoungcreatureinthreedays；andattimestheyoungvipereatsitswayoutfromtheinsideoftheegg。Themotherviperbringsforthallitsyounginoneday，twentyinnumber，andoneatatime。Theotherserpentsareexternallyoviparous，andtheireggsarestrungontooneanotherlikealady'snecklace；afterthedamhaslaidhereggsinthegroundshebroodsoverthem，andhatchestheeggsinthefollowingyear。
BookVI
1
Somuchforthegenerativeprocessesinsnakesandinsects，andalsoinoviparousquadrupeds。Birdswithoutexceptionlayeggs，butthepairingseasonandthetimesofparturitionarenotalikeforall。
Somebirdscoupleandlayatalmostanytimeintheyear，asforinstancethebarn-doorhenandthepigeon:theformerofthesecouplingandlayingduringtheentireyear，withtheexceptionofthemonthbeforeandthemonthafterthewintersolstice。Somehens，eveninthehighbreeds，layalargequantityofeggsbeforebrooding，amountingtoasmanyassixty；and，bytheway，thehigherbreedsarelessprolificthantheinferiorones。TheAdrianhensaresmall-sized，buttheylayeveryday；theyarecross-tempered，andoftenkilltheirchickens；theyareofallcolours。Somedomesticatedhenslaytwiceaday；indeed，instanceshavebeenknownwherehens，afterexhibitingextremefecundity，havediedsuddenly。
Hens，then，layeggs，ashasbeenstated，atalltimesindiscriminately；thepigeon，thering-dove，theturtle-dove，andthestock-dovelaytwiceayear，andthepigeonactuallylaystentimesayear。Thegreatmajorityofbirdslayduringthespring-time。Somebirdsareprolific，andprolificineitheroftwoways-eitherbylayingoften，asthepigeon，orbylayingmanyeggsatasitting，asthebarn-doorhen。Allbirdsofprey，orbirdswithcrookedtalons，areunprolific，exceptthekestrel:thisbirdisthemostprolificofbirdsofprey；asmanyasfoureggshavebeenobservedinthenest，andoccasionallyitlaysevenmore。
Birdsingenerallaytheireggsinnests，butsuchasaredisqualifiedforflight，asthepartridgeandthequail，donotlaytheminnestsbutontheground，andcoverthemoverwithloosematerial。Thesameisthecasewiththelarkandthetetrix。Thesebirdshatchinshelteredplaces；butthebirdcalledmeropsinBoeotia，aloneofallbirds，burrowsintoholesinthegroundandhatchesthere。
Thrushes，likeswallows，buildnestsofclay，onhightrees，andbuildtheminrowsallclosetogether，sothatfromtheircontinuitythestructureresemblesanecklaceofnests。Ofallbirdsthathatchforthemselvesthehoopoeistheonlyonethatbuildsnonestwhatever；itgetsintothehollowofthetrunkofatree，andlaysitseggstherewithoutmakinganysortofnest。Thecircusbuildseitherunderadwelling-rooforoncliffs。Thetetrix，calledouraxinAthens，buildsneitheronthegroundnorontrees，butonlow-lyingshrubs。
2
Theegginthecaseofallbirdsalikeishard-shelled，ifitbetheproduceofcopulationandbelaidbyahealthyhen-forsomehenslaysofteggs。Theinterioroftheeggisoftwocolours，andthewhitepartisoutsideandtheyellowpartwithin。
Theeggsofbirdsthatfrequentriversandmarshesdifferfromthoseofbirdsthatliveondryland；thatistosay，theeggsofwaterbirdshavecomparativelymoreoftheyelloworyolkandlessofthewhite。Eggsvaryincolouraccordingtotheirkind。Someeggsarewhite，asthoseofthepigeonandofthepartridge；othersareyellowish，astheeggsofmarshbirds；insomecasestheeggsaremottled，astheeggsoftheguinea-fowlandthepheasant；whiletheeggsofthekestrelarered，likevermilion。
Eggsarenotsymmetricallyshapedatbothends:inotherwords，oneendiscomparativelysharp，andtheotherendiscomparativelyblunt；anditisthelatterendthatprotrudesfirstatthetimeoflaying。Longandpointedeggsarefemale；thosethatareround，ormoreroundedatthenarrowend，aremale。Eggsarehatchedbytheincubationofthemother-bird。Insomecases，asinEgypt，theyarehatchedspontaneouslyintheground，bybeingburiedindungheaps。AstoryistoldofatoperinSyracuse，howheusedtoputeggsintothegroundunderhisrush-matandtokeepondrinkinguntilhehatchedthem。Instanceshaveoccurredofeggsbeingdepositedinwarmvesselsandgettinghatchedspontaneously。
Thespermofbirds，asofanimalsingeneral，iswhite。Afterthefemalehassubmittedtothemale，shedrawsupthespermtounderneathhermidriff。Atfirstitislittleinsizeandwhiteincolour；byandbyitisred，thecolourofblood；asitgrows，itbecomespaleandyellowallover。Whenatlengthitisgettingripeforhatching，itissubjecttodifferentiationofsubstance，andtheyolkgatherstogetherwithinandthewhitesettlesrounditontheoutside。Whenthefulltimeiscome，theeggdetachesitselfandprotrudes，changingfromsofttohardwithsuchtemporalexactitudethat，whereasitisnothardduringtheprocessofprotrusion，ithardensimmediatelyaftertheprocessiscompleted:thatisiftherebenoconcomitantpathologicalcircumstances。Caseshaveoccurredwheresubstancesresemblingtheeggatacriticalpointofitsgrowth-thatis，whenitisyellowallover，astheyolkissubsequently-havebeenfoundinthecockwhencutopen，underneathhismidriff，justwherethehenhashereggs；andtheseareentirelyyellowinappearanceandofthesamesizeasordinaryeggs。Suchphenomenaareregardedasunnaturalandportentous。
Suchasaffirmthatwind-eggsaretheresiduaofeggspreviouslybegottenfromcopulationaremistakeninthisassertion，forwehavecaseswellauthenticatedwherechickensofthecommonhenandgoosehavelaidwind-eggswithouteverhavingbeensubjectedtocopulation。Wind-eggsaresmaller，lesspalatable，andmoreliquidthantrueeggs，andareproducedingreaternumbers。Whentheyareputunderthemotherbird，theliquidcontentsnevercoagulate，butboththeyellowandthewhiteremainastheywere。Wind-eggsarelaidbyanumberofbirds:asforinstancebythecommonhen，thehenpartridge，thehenpigeon，thepeahen，thegoose，andthevulpanser。
Eggsarehatchedunderbroodinghensmorerapidlyinsummerthaninwinter；thatistosay，henshatchineighteendaysinsummer，butoccasionallyinwintertakeasmanyastwenty-five。Andbythewayforbroodingpurposessomebirdsmakebettermothersthanothers。Ifitthunderswhileahen-birdisbrooding，theeggsgetaddled。
Wind-eggsthatarecalledbysomecynosuraanduriaareproducedchieflyinsummer。Wind-eggsarecalledbysomezephyr-eggs，becauseatspring-timehen-birdsareobservedtoinhalethebreezes；theydothesameiftheybestrokedinapeculiarwaybyhand。Wind-eggscanturnintofertileeggs，andeggsduetopreviouscopulationcanchangebreed，ifbeforethechangeoftheyellowtothewhitethehenthatcontainswind-eggs，oreggsbegottenofcopulationbetroddenbyanothercock-bird。Underthesecircumstancesthewind-eggsturnintofertileeggs，andthepreviouslyimpregnatedeggsfollowthebreedoftheimpregnator；butifthelatterimpregnationtakesplaceduringthechangeoftheyellowtothewhite，thennochangeintheeggtakesplace:thewind-eggdoesnotbecomeatrueegg，andthetrueeggdoesnottakeonthebreedofthelatterimpregnator。Ifwhentheegg-substanceissmallcopulationbeintermitted，thepreviouslyexistingegg-substanceexhibitsnoincrease；butifthehenbeagainsubmittedtothemaletheincreaseinsizeproceedswithrapidity。
Theyolkandthewhitearediversenotonlyincolourbutalsoinproperties。Thus，theyolkcongealsundertheinfluenceofcold，whereasthewhiteinsteadofcongealingisinclinedrathertoliquefy。
Again，thewhitestiffensundertheinfluenceoffire，whereastheyolkdoesnotstiffen；but，unlessitbeburntthroughandthrough，itremainssoft，andinpointoffactisinclinedtosetortohardenmorefromtheboilingthanfromtheroastingoftheegg。Theyolkandthewhiteareseparatedbyamembranefromoneanother。Theso-called'hail-stones'，ortreadles，thatarefoundattheextremityoftheyellowinnowaycontributetowardsgeneration，assomeerroneouslysuppose:theyaretwoinnumber，onebelowandtheotherabove。Ifyoutakeoutoftheshellsanumberofyolksandanumberofwhitesandpourthemintoasaucepanandboilthemslowlyoveralowfire，theyolkswillgatherintothecentreandthewhiteswillsetallaroundthem。
Younghensarethefirsttolay，andtheydosoatthebeginningofspringandlaymoreeggsthantheolderhens，buttheeggsoftheyoungerhensarecomparativelysmall。Asageneralrule，ifhensgetnobroodingtheypineandsicken。Aftercopulationhensshiverandshakethemselves，andoftenkickrubbishaboutallroundthem-andthis，bytheway，theydosometimesafterlaying-whereaspigeonstrailtheirrumpsontheground，andgeesediveunderthewater。
Conceptionofthetrueeggandconformationofthewind-eggtakeplacerapidlywithmostbirds；asforinstancewiththehen-partridgewheninheat。Thefactisthat，whenshestandstowindwardandwithinscentofthemale，sheconceives，andbecomesuselessfordecoypurposes:for，bytheway，thepartridgeappearstohaveaveryacutesenseofsmell。
Thegenerationoftheeggaftercopulationandthegenerationofthechickfromthesubsequenthatchingoftheeggarenotbroughtaboutwithinequalperiodsforallbirds，butdifferastotimeaccordingtothesizeoftheparent-birds。Theeggofthecommonhenaftercopulationsetsandmaturesintendaysageneralrule；theeggofthepigeoninasomewhatlesserperiod。Pigeonshavethefacultyofholdingbacktheeggattheverymomentofparturition；
ifahenpigeonbeputaboutbyanyone，forinstanceifitbedisturbedonitsnest，orhaveafeatherpluckedout，orsustainanyotherannoyanceordisturbance，theneventhoughshehadmadeuphermindtolayshecankeeptheeggbackinabeyance。Asingularphenomenonisobservedinpigeonswithregardtopairing:thatis，theykissoneanotherjustwhenthemaleisonthepointofmountingthefemale，andwithoutthispreliminarythemalewoulddeclinetoperformhisfunction。Withtheoldermalesthepreliminarykissisonlygiventobeginwith，andsubsequentlysequentlyhemountswithoutpreviouslykissing；withyoungermalesthepreliminaryisneveromitted。Anothersingularityinthesebirdsisthatthehenstreadoneanotherwhenacockisnotforthcoming，afterkissingoneanotherjustastakesplaceinthenormalpairing。Thoughtheydonotimpregnateoneanothertheylaymoreeggsunderthesethanunderordinarycircumstances；nochicks，however，resulttherefrom，butallsucheggsarewind-eggs。
3
Generationfromtheeggproceedsinanidenticalmannerwithallbirds，butthefullperiodsfromconceptiontobirthdiffer，ashasbeensaid。Withthecommonhenafterthreedaysandthreenightsthereisthefirstindicationoftheembryo；withlargerbirdstheintervalbeinglonger，withsmallerbirdsshorter。Meanwhiletheyolkcomesintobeing，risingtowardsthesharpend，wheretheprimalelementoftheeggissituated，andwheretheegggetshatched；
andtheheartappears，likeaspeckofblood，inthewhiteoftheegg。
Thispointbeatsandmovesasthoughendowedwithlife，andfromittwovein-ductswithbloodinthemtrendinaconvolutedcourseastheeggsubstancegoesongrowing，towardseachofthetwocircumjacentinteguments；andamembranecarryingbloodyfibresnowenvelopstheyolk，leadingofffromthevein-ducts。Alittleafterwardsthebodyisdifferentiated，atfirstverysmallandwhite。Theheadisclearlydistinguished，andinittheeyes，swollenouttoagreatextent。Thisconditionoftheeyeslatonforagoodwhile，asitisonlybydegreesthattheydiminishinsizeandcollapse。Attheoutsettheunderportionofthebodyappearsinsignificantincomparisonwiththeupperportion。Ofthetwoductsthatleadfromtheheart，theoneproceedstowardsthecircumjacentintegument，andtheother，likeanavel-string，towardstheyolk。Thelife-elementofthechickisinthewhiteoftheegg，andthenutrimentcomesthroughthenavel-stringoutoftheyolk。
Whentheeggisnowtendaysoldthechickandallitspartsaredistinctlyvisible。Theheadisstilllargerthantherestofitsbody，andtheeyeslargerthanthehead，butstilldevoidofvision。
Theeyes，ifremovedaboutthistime，arefoundtobelargerthanbeans，andblack；ifthecuticlebepeeledoffthemthereisawhiteandcoldliquidinside，quiteglitteringinthesunlight，butthereisnohardsubstancewhatsoever。Suchistheconditionoftheheadandeyes。Atthistimealsothelargerinternalorgansarevisible，asalsothestomachandthearrangementoftheviscera；andveinsthatseemtoproceedfromtheheartarenowclosetothenavel。Fromthenaveltherestretchapairofveins；onetowardsthemembranethatenvelopstheyolkand，bytheway，theyolkisnowliquid，ormoresothanisnormal，andtheothertowardsthatmembranewhichenvelopscollectivelythemembranewhereinthechicklies，themembraneoftheyolk，andtheinterveningliquid。For，asthechickgrows，littlebylittleonepartoftheyolkgoesupward，andanotherpartdownward，andthewhiteliquidisbetweenthem；andthewhiteoftheeggisunderneaththelowerpartoftheyolk，asitwasattheoutset。Onthetenthdaythewhiteisattheextremeoutersurface，reducedinamount，glutinous，firminsubstance，andsallowincolour。
Thedispositionoftheseveralconstituentpartsisasfollows。Firstandoutermostcomesthemembraneoftheegg，notthatoftheshell，butunderneathit。Insidethismembraneisawhiteliquid；thencomesthechick，andamembraneroundaboutit，separatingitoffsoastokeepthechickfreefromtheliquid；nextafterthechickcomestheyolk，intowhichoneofthetwoveinswasdescribedasleading，theotheroneleadingintotheenvelopingwhitesubstance。Amembranewithaliquidresemblingserumenvelopstheentirestructure。Thencomesanothermembranerightroundtheembryo，ashasbeendescribed，separatingitoffagainsttheliquid。
Underneaththiscomestheyolk，envelopedinanothermembraneintowhichyolkproceedsthenavel-stringthatleadsfromtheheartandthebigvein，soastokeeptheembryofreeofbothliquids。
Aboutthetwentiethday，ifyouopentheeggandtouchthechick，itmovesinsideandchirps；anditisalreadycomingtobecoveredwithdown，when，afterthetwentiethdayisast，thechickbeginstobreaktheshell。Theheadissituatedovertherightlegclosetotheflank，andthewingisplacedoverthehead；andaboutthistimeisplaintobeseenthemembraneresemblinganafter-birththatcomesnextaftertheoutermostmembraneoftheshell，intowhichmembranetheoneofthenavel-stringswasdescribedasleadingand，bytheway，thechickinitsentiretyisnowwithinit，andsoalsoistheothermembraneresemblinganafter-birth，namelythatsurroundingtheyolk，intowhichthesecondnavel-stringwasdescribedasleading；andbothofthemweredescribedasbeingconnectedwiththeheartandthebigvein。Atthisconjuncturethenavel-stringthatleadstotheouterafterbirthcollapsesandbecomesdetachedfromthechick，andthemembranethatleadsintotheyolkisfastenedontothethingutofthecreature，andbythistimeaconsiderableamountoftheyolkisinsidethechickandayellowsedimentisinitsstomach。Aboutthistimeitdischargesresiduuminthedirectionoftheouterafter-birth，andhasresiduuminsideitsstomach；andtheouterresiduumiswhiteandtherecomesawhitesubstanceinside。Byandbytheyolk，diminishinggraduallyinsize，atlengthbecomesentirelyusedupandcomprehendedwithinthechicksothat，tendaysafterhatching，ifyoucutopenthechick，asmallremnantoftheyolkisstillleftinconnexionwiththegut，butitisdetachedfromthenavel，andthereisnothingintheintervalbetween，butithasbeenusedupentirely。Duringtheperiodabovereferredtothechicksleeps，wakesup，makesamoveandlooksupandChirps；andtheheartandthenaveltogetherpalpitateasthoughthecreaturewererespiring。Somuchastogenerationfromtheegginthecaseofbirds。
Birdslaysomeeggsthatareunfruitful，eveneggsthataretheresultofcopulation，andnolifecomesfromsucheggsbyincubation；andthisphenomenonisobservedespeciallywithpigeons。
Twineggshavetwoyolks。Insometwineggsathinpartitionofwhiteintervenestopreventtheyolksmixingwitheachother，butsometwineggsareunprovidedwithsuchpartition，andtheyokesrunintooneanother。Therearesomehensthatlaynothingbuttwineggs，andintheircasethephenomenonregardingtheyolkshasbeenobserved。Forinstance，ahenhasbeenknowntolayeighteeneggs，andtohatchtwinsoutofthemall，exceptthosethatwerewind-eggs；
therestwerefertilethough，bytheway，oneofthetwinsisalwaysbiggerthantheother，buttheeighteenthwasabnormalormonstrous。
4
Birdsofthepigeonkind，suchastheringdoveandtheturtle-dove，laytwoeggsatatime；thatistosay，theydosoasageneralrule，andtheyneverlaymorethanthree。Thepigeon，ashasbeensaid，laysatallseasons；thering-doveandtheturtle-dovelayinthespringtime，andtheyneverlaymorethantwiceinthesameseason。Thehen-birdlaysthesecondpairofeggswhenthefirstpairhappenstohavebeendestroyed，formanyofthehen-pigeonsdestroythefirstbrood。Thehen-pigeon，ashasbeensaid，occasionallylaysthreeeggs，butitneverrearsmorethantwochicks，andsometimesrearsonlyone；andtheoddoneisalwaysawind-egg。
Veryfewbirdspropagatewithintheirfirstyear。Allbirds，afteroncetheyhavebegunlaying，keeponhavingeggs，thoughinthecaseofsomebirdsitisdifficulttodetectthefactfromtheminutesizeofthecreature。
Thepigeon，asarule，laysamaleandafemaleegg，andgenerallylaysthemaleeggfirst；afterlayingitallowsaday'sintervaltoensueandthenlaysthesecondegg。Themaletakesitsturnofsittingduringthedaytime；thefemalesitsduringthenight。Thefirst-laideggishatchedandbroughttobirthwithintwentydays；andthemotherbirdpecksaholeintheeggthedaybeforeshehatchesitout。Thetwoparentbirdsbroodforsometimeoverthechicksinthewayinwhichtheybroodedpreviouslyovertheeggs。Inallconnectedwiththerearingoftheyoungthefemaleparentismorecross-temperedthanthemale，asisthecasewithmostanimalsafterparturition。Thehenslayasmanyastentimesintheyear；occasionalinstanceshavebeenknownoftheirlayingeleventimes，andinEgypttheyactuallylaytwelvetimes。Thepigeon，maleandfemale，coupleswithintheyear；infact，itcoupleswhenonlysixmonthsold。Someassertthatringdovesandturtle-dovespairandprocreatewhenonlythreemonthsold，andinstancetheirsuperabundantnumbersbywayofproofoftheassertion。Thehen-pigeoncarrieshereggsfourteendays；forasmanymoredaystheparentbirdshatchtheeggs；bytheendofanotherfourteendaysthechicksaresofarcapableofflightastobeovertakenwithdifficulty。Thering-dove，accordingtoallaccounts，livesuptofortyyears。Thepartridgelivesoversixteen。Afteronebroodthepigeonisreadyforanotherwithinthirtydays。
5
Thevulturebuildsitsnestoninaccessiblecliffs；forwhichreasonitsnestandyoungarerarelyseen。AndthereforeHerodorus，fatherofBrysontheSophist，declaresthatvulturesbelongtosomeforeigncountryunknowntous，statingasaproofoftheassertionthatnoonehaseverseenavulture'snest，andalsothatvulturesingreatnumbersmakeasuddenappearanceintherearofarmies。
However，difficultasitistogetasightofit，avulture'snesthasbeenseen。Thevulturelaystwoeggs。
Carnivorousbirdsingeneralareobservedtolaybutonceayear。Theswallowistheonlycarnivorousbirdthatbuildsanesttwice。Ifyouprickouttheeyesofswallowchickswhiletheyareyetyoung，thebirdswillgetwellagainandwillseebyandby。
6
Theeaglelaysthreeeggsandhatchestwoofthem，asitissaidintheversesascribedtoMusaeus:
Thatlaysthree，hatchestwo，andcaresforone。
Thisisthecaseinmostinstances，thoughoccasionallyabroodofthreehasbeenobserved。Astheyoungonesgrow，themotherbecomesweariedwithfeedingthemandextrudesoneofthepairfromthenest。Atthesametimethebirdissaidtoabstainfromfood，toavoidharryingtheyoungofwildanimals。Thatistosay，itswingsblanch，andforsomedaysitstalonsgetturnedawry。Itisinconsequenceaboutthistimecross-temperedtoitsownyoung。Thepheneissaidtoreartheyoungonethathasbeenexpelledthenest。Theeaglebroodsforaboutthirtydays。
Thehatchingperiodisaboutthesameforthelargerbirds，suchasthegooseandthegreatbustard；forthemiddle-sizedbirdsitextendsoverabouttwentydays，asinthecaseofthekiteandthehawk。Thekiteingenerallaystwoeggs，butoccasionallyrearsthreeyoungones。Theso-calledaegoliusattimesrearsfour。Itisnottruethat，assomeaver，theravenlaysonlytwoeggs；itlaysalargernumber。Itbroodsforabouttwentydaysandthenextrudesitsyoung。Otherbirdsperformthesameoperation；atalleventsmotherbirdsthatlayseveraleggsoftenextrudeoneoftheiryoung。
Birdsoftheeaglespeciesarenotalikeinthetreatmentoftheiryoung。Thewhite-tailedeagleiscross，theblackeagleisaffectionateinthefeedingoftheyoung；though，bytheway，allbirdsofprey，whentheirbroodisratherforwardinbeingabletofly，beatandextrudethemfromthenest。Themajorityofbirdsotherthanbirdsofprey，ashasbeensaid，alsoactinthismanner，andafterfeedingtheiryoungtakenofurthercareofthem；butthecrowisanexception。Thisbirdforaconsiderabletimetakeschargeofheryoung；for，evenwhenheryoungcanfly，shefliesalongsideofthemandsuppliesthemwithfood。
7
Thecuckooissaidbysometobeahawktransformed，becauseatthetimeofthecuckoo'scoming，thehawk，whichitresembles，isneverseen；andindeeditisonlyforafewdaysthatyouwillseehawksaboutwhenthecuckoo'snotesoundsearlyintheseason。Thecuckooappearsonlyforashorttimeinsummer，andinwinterdisappears。Thehawkhascrookedtalons，whichthecuckoohasnot；
neitherwithregardtotheheaddoesthecuckooresemblethehawk。
Inpointoffact，bothasregardstheheadandtheclawsitmoreresemblesthepigeon。However，incolourandincolouraloneitdoesresemblethehawk，onlythatthemarkingsofthehawkarestriped，andofthecuckoomottled。And，bytheway，insizeandflightitresemblesthesmallestofthehawktribe，whichbirddisappearsasaruleaboutthetimeoftheappearanceofthecuckoo，thoughthetwohavebeenseensimultaneously。Thecuckoohasbeenseentobepreyedonbythehawk；andthisneverhappensbetweenbirdsofthesamespecies。Theysaynoonehaseverseentheyoungofthecuckoo。Thebirdeggs，butdoesnotbuildanest。Sometimesitlaysitseggsinthenestofasmallerbirdafterfirstdevouringtheeggsofthisbird；itlaysbypreferenceinthenestoftheringdove，afterfirstdevouringtheeggsofthepigeon。Itoccasionallylaystwo，butusuallyone。Itlaysalsointhenestofthehypolais，andthehypolaishatchesandrearsthebrood。Itisaboutthistimethatthebirdbecomesfatandpalatable。Theyoungofhawksalsogetpalatableandfat。Onespeciesbuildsanestinthewildernessandonsheerandinaccessiblecliffs。
8
Withmostbirds，ashasbeensaidofthepigeon，thehatchingiscarriedonbythemaleandthefemaleinturns:withsomebirds，however，themaleonlysitslongenoughtoallowthefemaletoprovideherselfwithfood。Inthegoosetribethefemalealoneincubates，andafteroncesittingontheeggsshecontinuesbroodinguntiltheyarehatched。
Thenestsofallmarsh-birdsarebuiltindistrictsfennyandwellsuppliedwithgrass；consequently，themother-birdwhilesittingquietonhereggscanprovideherselfwithfoodwithouthavingtosubmittoabsolutefasting。
Withthecrowalsothefemalealonebroods，andbroodsthroughoutthewholeperiod；themalebirdsupportsthefemale，bringingherfoodandfeedingher。Thefemaleofthering-dovebeginstobroodintheafternoonandbroodsthroughtheentirenightuntilbreakfast-timeofthefollowingday；themalebroodsduringtherestofthetime。Partridgesbuildanestintwocompartments；themalebroodsontheoneandthefemaleontheother。Afterhatching，eachoftheparentbirdsrearsitsbrood。Butthemale，whenhefirsttakeshisyoungoutofthenest，treadsthem。
9
Peafowlliveforabouttwenty-fiveyears，breedaboutthethirdyear，andatthesametimetakeontheirspangledplumage。Theyhatchtheireggswithinthirtydaysorrathermore。Thepeahenlaysbutonceayear，andlaystwelveeggs，ormaybeaslightlylessernumber:shedoesnotlayalltheeggsthereandthenoneaftertheother，butatintervalsoftwoorthreedays。Suchaslayforthefirsttimelayabouteighteggs。Thepeahenlayswind-eggs。Theypairinthespring；andlayingbeginsimmediatelyafterpairing。Thebirdmoultswhentheearliesttreesaresheddingtheirleaves，andrecoversitsplumagewhenthesametreesarerecoveringtheirfoliage。
Peoplethatrearpeafowlputtheeggsunderthebarn-doorhen，owingtothefactthatwhenthepeahenisbroodingoverthemthepeacockattacksherandtriestotrampleonthem；owingtothiscircumstancesomebirdsofwildvarietiesrunawayfromthemalesandlaytheireggsandbroodinsolitude。Onlytwoeggsareputunderabarn-doorhen，forshecouldnotbroodoverandhatchalargenumber。Theytakeeveryprecaution，bysupplyingherwithfood，topreventhergoingofftheeggsanddiscontinuingthebrooding。
Withmalebirdsaboutpairingtimethetesticlesareobviouslylargerthanatothertimes，andthisisconspicuouslythecasewiththemoresalaciousbirds，suchasthebarn-doorcockandthecockpartridge；thepeculiarityislessconspicuousinsuchbirdsasareintermittentinregardtopairing。
10
Somuchfortheconceptionandgenerationofbirds。
Ithasbeenpreviouslystatedthatfishesarenotalloviparous。
Fishesofthecartilaginousgenusareviviparous；therestareoviparous。Andcartilaginousfishesarefirstoviparousinternallyandsubsequentlyviviparous；theyreartheembryosinternally，thebatrachusorfishing-frogbeinganexception。
Fishesalso，aswasabovestated，areprovidedwithwombs，andwombsofdiversekinds。Theoviparousgenerahavewombsbifurcateinshapeandlowdowninposition；thecartilaginousgenushavewombsshapedlikethoseofObirds。Thewomb，however，inthecartilaginousfishesdiffersinthisrespectfromthewombofbirds，thatwithsomecartilaginousfishestheeggsdonotsettleclosetothediaphragmbutmiddle-waysalongthebackbone，andastheygrowtheyshifttheirposition。
Theeggwithallfishesisnotoftwocolourswithinbutisofevenhue；andthecolourisnearertowhitethantoyellow，andthatbothwhentheyoungisinsideitandpreviouslyaswell。
Developmentfromtheegginfishesdiffersfromthatinbirdsinthisrespect，thatitdoesnotexhibitthatoneofthetwonavel-stringsthatleadsofftothemembranethatliescloseundertheshell，whileitdoesexhibitthatoneofthetwothatinthecaseofbirdsleadsofftotheyolk。Inageneralwaytherestofthedevelopmentfromtheeggonwardsisidenticalinbirdsandfishes。
Thatistosay，developmenttakesplaceattheupperpartoftheegg，andtheveinsextendinlikemanner，atfirstfromtheheart；andatfirstthehead，theeyes，andtheupperpartsarelargest；andasthecreaturegrowstheegg-substancedecreasesandeventuallydisappears，andbecomesabsorbedwithintheembryo，justastakesplacewiththeyolkinbirds。
Thenavel-stringisattachedalittlewaybelowtheapertureofthebelly。Whenthecreaturesareyoungthenavel-stringislong，butastheygrowitdiminishesinsize；atlengthitgetssmallandbecomesincorporated，aswasdescribedinthecaseofbirds。Theembryoandtheeggareenvelopedbyacommonmembrane，andjustunderthisisanothermembranethatenvelopstheembryobyitself；andinbetweenthetwomembranesisaliquid。Thefoodinsidethestomachofthelittlefishesresemblesthatinsidethestomachofyoungchicks，andispartlywhiteandpartlyyellow。
Asregardstheshapeofthewomb，thereaderisreferredtomytreatiseonAnatomy。Thewomb，however，isdiverseindiversefishes，asforinstanceinthesharksascomparedonewithanotherorascomparedwiththeskate。Thatistosay，insomesharkstheeggsadhereinthemiddleofthewombroundaboutthebackbone，ashasbeenstated，andthisisthecasewiththedog-fish；astheeggsgrowtheyshifttheirplace；andsincethewombisbifurcateandadherestothemidriff，asintherestofsimilarcreatures，theeggspassintooneorotherofthetwocompartments。Thiswombandthewomboftheothersharksexhibit，asyougoalittlewayofffromthemidriff，somethingresemblingwhitebreasts，whichnevermaketheirappearanceunlesstherebeconception。
Dog-fishandskatehaveakindofegg-shell，inthewhichisfoundanegg-likeliquid。Theshapeoftheegg-shellresemblesthetongueofabagpipe，andhair-likeductsareattachedtotheshell。
Withthedog-fishwhichiscalledbysomethe'dappledshark'，theyoungarebornwhentheshell-formationbreaksinpiecesandfallsout；withtheray，afterithaslaidtheeggtheshell-formationbreaksupandtheyoungmoveout。Thespinydog-fishhasitsclosetothemidriffabovethebreastlikeformations；whentheeggdescends，assoonasitgetsdetachedtheyoungisborn。Themodeofgenerationisthesameinthecaseofthefox-shark。
Theso-calledsmoothsharkhasitseggsinbetwixtthewombslikethedog-fish；theseeggsshiftintoeachofthetwohornsofthewombanddescend，andtheyoungdevelopwiththenavel-stringattachedtothewomb，sothat，astheegg-substancegetsusedup，theembryoissustainedtoallappearancejustasinthecaseofquadrupeds。Thenavel-stringislongandadherestotheunderpartofthewombeachnavel-stringbeingattachedasitwerebyasucker，andalsotothecentreoftheembryointheplacewheretheliverissituated。Iftheembryobecutopen，eventhoughithastheegg-substancenolonger，thefoodinsideisegg-likeinappearance。
Eachembryo，asinthecaseofquadrupeds，isprovidedwithachorionandseparatemembranes。Whenyoungtheembryohasitsheadupwards，butdownwardswhenitgetsstrongandiscompletedinform。
Malesaregeneratedontheleft-handsideofthewomb，andfemalesontheright-handside，andmalesandfemalesonthesamesidetogether。Iftheembryobecutopen，then，aswithquadrupeds，suchinternalorgansasitisfurnishedwith，asforinstancetheliver，arefoundtobelargeandsuppliedwithblood。
Allcartilaginousfisheshaveatoneandthesametimeeggsaboveclosetothemidriffsomelarger，somesmaller，inconsiderablenumbers，andalsoembryoslowerdown。Andthiscircumstanceleadsmanytosupposethatfishesofthisspeciespairandbearyoungeverymonth，inasmuchastheydonotproducealltheiryoungatonce，butnowandagainandoveralengthenedperiod。
Butsucheggsashavecomedownbelowwithinthewombaresimultaneouslyripenedandcompletedingrowth。
Dog-fishingeneralcanextrudeandtakeinagaintheiryoung，ascanalsotheangel-fishandtheelectricray-and，bytheway，alargeelectricrayhasbeenseenwithabouteightyembryosinsideit-butthespinydogfishisanexceptiontotherule，beingpreventedbythespineoftheyoungfishfromsodoing。Oftheflatcartilaginousfish，thetrygonandtheraycannotextrudeandtakeinagaininconsequenceoftheroughnessofthetailsoftheyoung。
Thebatrachusorfishing-frogalsoisunabletotakeinitsyoungowingtothesizeoftheheadandtheprickles；and，bytheway，aswaspreviouslyremarked，itistheonlyoneofthesefishesthatisnotviviparous。
Somuchforthevarietiesofthecartilaginousspeciesandfortheirmodesofgenerationfromtheegg。
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Atthebreedingseasonthesperm-ductsofthemalearefilledwithsperm，somuchsothatiftheybesqueezedthespermflowsoutspontaneouslyasawhitefluid；theductsarebifurcate，andstartfromthemidriffandthegreatvein。Aboutthisperiodthesperm-ductsofthemalearequitedistinctfromthewombofthefemalebutatanyotherthantheactualbreedingtimetheirdistinctnessisnotobvioustoanon-expert。Thefactisthatincertainfishesatcertaintimestheseorgansareimperceptible，aswasstatedregardingthetesticlesofbirds。
Amongotherdistinctionsobservedbetweenthethoricductsandthewomb-ductsisthecircumstancethatthethoricductsareattachedtotheloins，whilethewomb-ductsmoveaboutfreelyandareattachedbyathinmembrane。TheparticularsregardingthethoricductsmaybestudiedbyareferencetothediagramsinmytreatiseonAnatomy。
Cartilaginousfishesarecapableofsuperfoetation，andtheirperiodofgestationissixmonthsatthelongest。Theso-calledstarrydogfishbearsyoungthemostfrequently；inotherwordsitbearstwiceamonth。ThebreedingseasonisinthemonthofMaemacterion。Thedog-fishasageneralrulebeartwiceintheyear，withtheexceptionofthelittledog-fish，whichbearsonlyonceayear。Someofthembringforthinthespringtime。Therhine，orangel-fish，bearsitsfirstbroodinthespringtime，anditssecondintheautumn，aboutthewintersettingofthePleiads；thesecondbroodisthestrongerofthetwo。Theelectricraybringsforthinthelateautumn。
Cartilaginousfishescomeoutfromthemainseasanddeepwaterstowardstheshoreandtherebringforththeiryoung，andtheydosoforthesakeofwarmthandbywayofprotectionfortheiryoung。
Observationswouldleadtothegeneralrulethatnoonevarietyoffishpairswithanothervariety。Theangel-fish，however，andthebatusorskateappeartopairwithoneanother；forthereisafishcalledtherhinobatus，withtheheadandfrontpartsoftheskateandtheafterpartsoftherhineorangel-fish，justasthoughitweremadeupofbothfishestogether。
Sharksthenandtheircongeners，asthefox-sharkandthedog-fish，andtheflatfishes，suchastheelectricray，theray，thesmoothskate，andthetrygon，arefirstoviparousandthenviviparousinthewayabovementioned，asarealsothesaw-fishandtheox-ray。
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Thedolphin，thewhale，andalltherestoftheCetacea，all，thatistosay，thatareprovidedwithablow-holeinsteadofgills，areviviparous。Thatistosay，nooneofallthesefishesiseverseentobesuppliedwitheggs，butdirectlywithanembryofromwhosedifferentiationcomesthefish，justasinthecaseofmankindandtheviviparousquadrupeds。
Thedolphinbearsoneatatimegenerally，butoccasionallytwo。
Thewhalebearsoneoratthemosttwo，generallytwo。Theporpoiseinthisrespectresemblesthedolphin，and，bytheway，itisinformlikealittledolphin，andisfoundintheEuxine；itdiffers，however，fromthedolphinasbeinglessinsizeandbroaderintheback；itscolourisleaden-black。Manypeopleareofopinionthattheporpoiseisavarietyofthedolphin。
Allcreaturesthathaveablow-holerespireandinspire，fortheyareprovidedwithlungs。Thedolphinhasbeenseenasleepwithhisnoseabovewater，andwhenasleephesnores。
Thedolphinandtheporpoiseareprovidedwithmilk，andsuckletheiryoung。Theyalsotaketheiryoung，whensmall，insidethem。Theyoungofthedolphingrowrapidly，beingfullgrownattenyearsofage。Itsperiodofgestationistenmonths。Itbringsforthitsyoungsummer，andneveratanyotherseason；and，singularlyenough，undertheDogstaritdisappearsforaboutthirtydays。Itsyoungaccompanyitforaconsiderableperiod；and，infact，thecreatureisremarkableforthestrengthofitsparentalaffection。
Itlivesformanyyears；someareknowntohavelivedformorethantwenty-five，andsomeforthirtyyears；thefactisfishermennicktheirtailssometimesandsetthemadriftagain，andbythisexpedienttheiragesareascertained。
Thesealisanamphibiousanimal:thatistosay，itcannottakeinwater，butbreathesandsleepsandbringsforthondryland-onlyclosetotheshore-asbeingananimalfurnishedwithfeet；itspends，however，thegreaterpartofitstimeintheseaandderivesitsfoodfromit，sothatitmustbeclassedinthecategoryofmarineanimals。Itisviviparousbyimmediateconceptionandbringsforthitsyoungalive，andexhibitsanafter-birthandallelsejustlikeaewe。
Itbearsoneortwoatatime，andthreeatthemost。Ithastwoteats，andsucklesitsyounglikeaquadruped。Likethehumanspeciesitbringsforthatallseasonsoftheyear，butespeciallyatthetimewhentheearliestkidsareforthcoming。Itconductsitsyoungones，whentheyareabouttwelvedaysold，overandoveragainduringthedaydowntothesea，accustomingthembyslowdegreestothewater。Itslipsdownsteepplacesinsteadofwalking，fromthefactthatitcannotsteadyitselfbyitsfeet。Itcancontractanddrawitselfin，foritisfleshyandsoftanditsbonesaregristly。
Owingtotheflabbinessofitsbodyitisdifficulttokillasealbyablow，unlessyoustrikeitonthetemple。Itlookslikeacow。
Thefemaleinregardtoitsgenitalorgansresemblesthefemaleoftheray；inallotherrespectsitresemblesthefemaleofthehumanspecies。
Somuchforthephenomenaofgenerationandofparturitioninanimalsthatliveinwaterandareviviparouseitherinternallyorexternally。
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Oviparousfisheshavetheirwombbifurcateandplacedlowdown，aswassaidpreviously-and，bytheway，allscalyfishareoviparous，asthebasse，themullet，thegreymullet，andtheetelis，andalltheso-calledwhite-fish，andallthesmoothorslipperyfishexcepttheeel-andtheirroeisofacrumblingorgranularsubstance。Thisappearanceisduetothefactthatthewholewombofsuchfishesisfullofeggs，sothatinlittlefishesthereseemtobeonlyacoupleofeggsthere；forinsmallfishesthewombisindistinguishable，fromitsdiminutivesizeandthincontexture。Thepairingoffisheshasbeendiscussedpreviously。
Fishesforthemostpartaredividedintomalesandfemales，butoneispuzzledtoaccountfortheerythrinusandthechanna，forspecimensofthesespeciesarenevercaughtexceptinaconditionofpregnancy。
Withsuchfishaspair，eggsaretheresultofcopulation，butsuchfishhavethemalsowithoutcopulation；andthisisshowninthecaseofsomeriver-fish，fortheminnowhaseggswhenquitesmall，-almost，onemaysay，assoonasitisborn。Thesefishesshedtheireggslittlebylittle，and，asisstated，themalesswallowthegreaterpartofthem，andsomeportionofthemgoestowasteinthewater；butsuchoftheeggsasthefemaledepositsonthespawningbedsaresaved。Ifalltheeggswerepreserved，eachspecieswouldbeinfiniteinnumber。Thegreaternumberoftheseeggssodepositedarenotproductive，butonlythoseoverwhichthemaleshedsthemiltorsperm；forwhenthefemalehaslaidhereggs，themalefollowsandshedsitsspermoverthem，andfromalltheeggssobesprinkledyoungfishesproceed，whiletherestarelefttotheirfate。
Thesamephenomenonisobservedinthecaseofmolluscsalso；
forinthecaseofthecuttlefishorsepia，afterthefemalehasdepositedhereggs，themalebesprinklesthem。Itishighlyprobablethatasimilarphenomenontakesplaceinregardtomolluscsingeneral，thoughuptothepresenttimethephenomenonhasbeenobservedonlyinthecaseofthecuttlefish。
Fishesdeposittheireggscloseintoshore，thegobyclosetostones；and，bytheway，thespawnofthegobyisflatandcrumbly。
Fishingeneralsodeposittheireggs；forthewatercloseintoshoreiswarmandisbettersuppliedwithfoodthantheoutersea，andservesasaprotectiontothespawnagainstthevoracityofthelargerfish。AnditisforthisreasonthatintheEuxinemostfishesspawnnearthemouthoftheriverThermodon，becausethelocalityissheltered，genial，andsuppliedwithfreshwater。
Oviparousfishasarulespawnonlyonceayear。Thelittlephycisorblackgobyisanexception，asitspawnstwice；themaleoftheblackgobydiffersfromthefemaleasbeingblackerandhavinglargerscales。
Fishestheningeneralproducetheiryoungbycopulation，andlaytheireggs；butthepipefish，assomecallit，whenthetimeofparturitionarrives，burstsintwo，andtheeggsescapeout。Forthefishhasadiaphysisorclovengrowthunderthebellyandabdomenliketheblindsnakes，and，afterithasspawnedbythesplittingofthisdiaphysis，thesidesofthesplitgrowtogetheragain。
Developmentfromtheeggtakesplacesimilarlywithfishesthatareoviparousinternallyandwithfishesthatareoviparousexternally；thatistosay，theembryocomesattheupperendoftheeggandisenvelopedinamembrane，andtheeyes，largeandspherical，arethefirstorgansvisible。Fromthiscircumstanceitisplainthattheassertionisuntenablewhichismadebysomewriters，towit，thattheyoungofoviparousfishesaregeneratedlikethegrubsofworms；fortheoppositephenomenaareobservedinthecaseofthesegrubs，inthattheirlowerextremitiesarethelargerattheoutset，andthattheeyesandtheheadappearlateron。Aftertheegghasbeenusedup，theyoungfishesareliketadpolesinshape，andatfirst，withouttakinganynutriment，theygrowbysustenancederivedfromthejuiceoozingfromtheegg；byandby，theyarenourisheduptofullgrowthbytheriver-waters。
WhentheEuxineis'purged'asubstancecalledphycusiscarriedintotheHellespont，andthissubstanceisofapaleyellowcolour。
Somewritersaverthatitistheflowerofthephycus，fromwhichrougeismade；itcomesatthebeginningofsummer。Oystersandthesmallfishoftheselocalitiesfeedonthissubstance，andsomeoftheinhabitantsofthesemaritimedistrictssaythatthepurplemurexderivesitspeculiarcolourfromit。
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Marsh-fishesandriver-fishesconceiveattheageoffivemonthsasageneralrule，anddeposittheirspawntowardsthecloseoftheyearwithoutexception。Andwiththesefishes，likeaswiththemarinefishes，thefemaledoesnotvoidallhereggsatonetime，northemalehissperm；buttheyareatalltimesmoreorlessprovided，thefemalewitheggs，andthemalewithsperm。The-carpspawnsastheseasonscomeround，fiveorsixtimes，andfollowsinspawningtherisingofthegreaterconstellations。Thechalcisspawnsthreetimes，andtheotherfishesonceonlyintheyear。Theyallspawninpoolsleftbytheoverflowingofrivers，andneartoreedyplacesinmarshes；asforinstancethephoxinusorminnowandtheperch。
Theglanisorsheat-fishandtheperchdeposittheirspawninonecontinuousstring，likethefrog；socontinuous，infact，istheconvolutedspawnoftheperchthat，byreasonofitssmoothness，thefishermeninthemarshescanunwinditoffthereedslikethreadsoffareel。Thelargerindividualsofthesheat-fishspawnindeepwaters，someinwaterofafathom'sdepth，thesmallerinshallowerwater，generallyclosetotherootsofthewilloworofsomeothertree，orclosetoreedsortomoss。Attimesthesefishesintertwinewithoneanother，abigwithalittleone，andbringintojuxtapositiontheducts-whichsomewritersdesignateasnavels-atthepointwheretheyemitthegenerativeproductsanddischargetheegginthecaseofthefemaleandthemiltinthecaseofthemale。
Sucheggsasarebesprinkledwiththemiltgrow，inadayorthereabouts，whiterandlarger，andinalittlewhileafterwardsthefish'seyesbecomevisiblefortheseorgansinallfishes，asforthatmatterinallotheranimals，areearlyconspicuousandseemdisproportionatelybig。Butsucheggsasthemiltfailstotouchremain，aswithmarinefishes，uselessandinfertile。Fromthefertileeggs，asthelittlefishgrow，akindofsheathdetachesitself；
thisisamembranethatenvelopstheeggandtheyoungfish。Whenthemilthasmingledwiththeeggs，theresultingproductbecomesverystickyorviscous，andadherestotherootsoftreesorwhereveritmayhavebeenlaid。Themalekeepsonguardattheprincipalspawning-place，andthefemaleafterspawninggoesaway。
Inthecaseofthesheat-fishthegrowthfromtheeggisexceptionallyslow，and，inconsequence，themalehastokeepwatchforfortyorfiftydaystopreventthe-spawnbeingdevouredbysuchlittlefishesaschancetocomeby。Nextinpointofslownessisthegenerationofthecarp。Aswithfishesingeneral，soevenwiththese，thespawnthusprotecteddisappearsandgetslostrapidly。
Inthecaseofsomeofthesmallerfisheswhentheyareonlythreedaysoldyoungfishesaregenerated。Eggstouchedbythemalespermtakeonincreaseboththesamedayandalsolater。Theeggofthesheat-fishisasbigasavetch-seed；theeggofthecarpandofthecarp-speciesasbigasamillet-seed。
Thesefishesthenspawnandgenerateinthewayheredescribed。Thechalcis，however，spawnsindeepwaterindenseshoalsoffish；andtheso-calledtilonspawnsneartobeachesinshelteredspotsinshoalslikewise。Thecarp，thebaleros，andfishesingeneralpusheagerlyintotheshallowsforthepurposeofspawning，andveryoftenthirteenorfourteenmalesareseenfollowingasinglefemale。Whenthefemaledepositsherspawnanddeparts，themalesfollowonandshedthemilt。Thegreaterportionofthespawngetswasted；because，owingtothefactthatthefemalemovesaboutwhilespawning，thespawnscatters，orsomuchofitasiscaughtinthestreamanddoesnotgetentangledwithsomerubbish。For，withtheexceptionofthesheatfish，nofishkeepsonguard；unless，bytheway，itbethecarp，whichissaidtoremainonguard，ifitsohappenthatitsspawnliesinasolidmass。
Allmalefishesaresuppliedwithmilt，exceptingtheeel:withtheeel，themaleisdevoidofmilt，andthefemaleofspawn。Themulletgoesupfromtheseatomarshesandrivers；theeels，onthecontrary，maketheirwaydownfromthemarshesandriverstothesea。
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Thegreatmajorityoffish，then，ashasbeenstated，proceedfromeggs。However，therearesomefishthatproceedfrommudandsand，evenofthosekindsthatproceedalsofrompairingandtheegg。Thisoccursinpondshereandthere，andespeciallyinapondintheneighbourhoodofCnidos。Thispond，itissaid，atonetimerandryabouttherisingoftheDogstar，andthemudhadalldriedup；atthefirstfalloftherainstherewasashowofwaterinthepond，andonthefirstappearanceofthewatershoalsoftinyfishwerefoundinthepond。Thefishinquestionwasakindofmullet，onewhichdoesnotproceedfromnormalpairing，aboutthesizeofasmallsprat，andnotoneofthesefisheswasprovidedwitheitherspawnormilt。
TherearefoundalsoinAsiaMinor，inriversnotcommunicatingwiththesea，littlefisheslikewhitebait，differingfromthesmallfryfoundnearCnidosbutfoundundersimilarcircumstances。Somewritersactuallyaverthatmulletallgrowspontaneously。Inthisassertiontheyaremistaken，forthefemaleofthefishisfoundprovidedwithspawn，andthemalewithmilt。However，thereisaspeciesofmulletthatgrowsspontaneouslyoutofmudandsand。
Fromthefactsaboveenumerateditisquiteprovedthatcertainfishescomespontaneouslyintoexistence，notbeingderivedfromeggsorfromcopulation。Suchfishasareneitheroviparousnorviviparousariseallfromoneoftwosources，frommud，orfromsandandfromdecayedmatterthatrisesthenceasascum；forinstance，theso-calledfrothofthesmallfrycomesoutofsandyground。Thisfryisincapableofgrowthandofpropagatingitskind；afterlivingforawhileitdiesawayandanothercreaturetakesitsplace，andso，withshortintervalsexcepted，itmaybesaidtolastthewholeyearthrough。Atallevents，itlastsfromtheautumnrisingofArcturusuptothespring-time。Asaproofthatthesefishoccasionallycomeoutofthegroundwehavethefactthatincoldweathertheyarenotcaught，andthattheyarecaughtinwarmweather，obviouslycomingupoutofthegroundtocatchtheheat；also，whenthefishermenusedredgesandthegroundisscrapedupfairlyoften，thefishesappearinlargernumbersandofsuperiorquality。Allothersmallfryareinferiorinqualityowingtorapidityofgrowth。Thefryarefoundinshelteredandmarshydistricts，whenafteraspelloffineweatherthegroundisgettingwarmer，as，forinstance，intheneighbourhoodofAthens，atSalamisandnearthetombofThemistoclesandatMarathon；forinthesedistrictsthefrothisfound。Itappears，then，insuchdistrictsandduringsuchweather，andoccasionallyappearsafteraheavyfallofraininthefroththatisthrownupbythefallingrain，fromwhichcircumstancethesubstancederivesitsspecificname。Foamisoccasionallybroughtinonthesurfaceoftheseainfairweather。Andinthis，whereithasformedonthesurface，theso-calledfrothcollects，asgrubsswarminmanure；forwhich-reasonthisfryisoftenbroughtinfromtheopensea。Thefishisatitsbestinqualityandquantityinmoistwarmweather。
Theordinaryfryisthenormalissueofparentfishes:theso-calledgudgeon-fryofsmallinsignificantgudgeon-likefishthatburrowundertheground。FromthePhalericfrycomesthemembras，fromthemembrasthetrichis，fromthetrichisthetrichias，andfromoneparticularsortoffry，towitfromthatfoundintheharbourofAthens，comeswhatiscalledtheencrasicholus，oranchovy。Thereisanotherfry，derivedfromthemaenisandthemullet。
Theunfertilefryiswateryandkeepsonlyashorttime，ashasbeenstated，foratlastonlyheadandeyesareleft。However，thefishermenoflatehavehituponamethodoftransportingittoadistance，aswhensalteditkeepsforaconsiderabletime。
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Eelsarenottheissueofpairing，neitheraretheyoviparous；norwasaneeleverfoundsuppliedwitheithermiltorspawn，noraretheywhencutopenfoundtohavewithinthempassagesforspawnorforeggs。Inpointoffact，thisentirespeciesofbloodedanimalsproceedsneitherfrompairnorfromtheegg。
Therecanbenodoubtthatthecaseisso。Forinsomestandingpools，afterthewaterhasbeendrainedoffandthemudhasbeendredgedaway，theeelsappearagainafterafallofrain。Intimeofdroughttheydonotappeareveninstagnantponds，forthesimplereasonthattheirexistenceandsustenanceisderivedfromrain-water。
Thereisnodoubt，then，thattheyproceedneitherfrompairingnorfromanegg。Somewriters，however，areofopinionthattheygeneratetheirkind，becauseinsomeeelslittlewormsarefound，fromwhichtheysupposethateelsarederived。Butthisopinionisnotfoundedonfact。Eelsarederivedfromtheso-called'earth'sguts'
thatgrowspontaneouslyinmudandinhumidground；infact，eelshaveattimesbeenseentoemergeoutofsuchearthworms，andonotheroccasionshavebeenrenderedvisiblewhentheearthwormswerelaidopenbyeitherscrapingorcutting。Suchearthwormsarefoundbothintheseaandinrivers，especiallywherethereisdecayedmatter:intheseainplaceswheresea-weedabounds，andinriversandmarshesneartotheedge；foritisneartothewater'sedgethatsun-heathasitschiefpowerandproducesputrefaction。Somuchforthegenerationoftheeel。
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Fishdonotallbringforththeiryoungatthesameseasonnorallinlikemanner，neitheristheperiodofgestationforallofthesameduration。
Beforepairingthemalesandfemalesgathertogetherinshoals；atthetimeforcopulationandparturitiontheypairoff。Withsomefishesthetimeofgestationisnotlongerthanthirtydays，withothersitisalesserperiod；butwithallitextendsoveranumberofdaysdivisiblebyseven。Thelongestperiodofgestationisthatofthespecieswhichsomecallamarinus。
ThesargueconceivesduringthemonthofPoseideonorDecember，andcarriesitsspawnforthirtydays；andthespeciesofmulletnamedbysomethechelon，andthemyxon，gowithspawnatthesameperiodandoverthesamelengthoftime。
Allfishsuffergreatlyduringtheperiodofgestation，andareinconsequenceveryapttobethrownuponshoreatthistime。
Insomecasestheyaredrivenfranticwithpainandthrowthemselvesonland。Atalleventstheyarethroughoutthistimecontinuallyinmotionuntilparturitionisoverthisbeingespeciallytrueofthemullet，andafterparturitiontheyareinrepose。Withmanyfishthetimeforparturitionterminatesontheappearanceofgrubswithinthebelly；forsmalllivinggrubsgetgeneratedthereandeatupthespawn。
Withshoalfishesparturitiontakesplaceinthespring，andindeed，withmostfishes，aboutthetimeofthespringequinox；withothersitisatdifferenttimes，insummerwithsome，andwithothersabouttheautumnequinox。
Thefirstofshoalfishestospawnistheatherine，anditspawnsclosetoland；thelastisthecephalus:andthisisinferredfromthefactthatthebroodoftheatherineappearsfirstofallandthebroodofthecephaluslast。Themulletalsospawnsearly。
Thesaupespawnsusuallyatthebeginningofsummer，butoccasionallyintheautumn。Theaulopias，whichsomecalltheanthias，spawnsinthesummer。Nextinorderofspawningcomesthechrysophrysorgilthead，thebasse，themormyrus，andingeneralsuchfishasarenicknamed'runners'。Latestinorderoftheshoalfishcometheredmulletandthecoracine；thesespawninautumn。
Theredmulletspawnsonmud，andconsequently，asthemudcontinuescoldforalongwhile，spawnslateintheyear。Thecoracinecarriesitsspawnforalongtime；but，asitlivesusuallyonrockyground，itgoestoadistanceandspawnsinplacesaboundinginseaweed，ataperiodlaterthantheredmullet。Themaenisspawnsaboutthewintersolstice。Oftheothers，suchasarepelagicspawnforthemostpartinsummer；whichfactisprovedbytheirnotbeingcaughtbyfishermenduringthisperiod。
Ofordinaryfishesthemostprolificisthesprat；ofcartilaginousfishes，thefishing-frog。Specimens，however，ofthefishing-frogarerarefromthefacilitywithwhichtheyoungaredestroyed，asthefemalelaysherspawnallinalumpcloseintoshore。Asarule，cartilaginousfisharelessprolificthanotherfishowingtotheirbeingviviparous；andtheiryoungbyreasonoftheirsizehaveabetterchanceofescapingdestruction。
Theso-calledneedle-fishorpipe-fishislateinspawning，andthegreaterportionofthemareburstasunderbytheeggsbeforespawning；andtheeggsarenotsomanyinnumberaslargeinsize。Theyoungfishclusterroundtheparentlikesomanyyoungspiders，forthefishspawnsontoherself；and，ifanyonetouchtheyoung，theyswimaway。Theatherinespawnsbyrubbingitsbellyagainstthesand。
Tunnyfishalsoburstasunderbyreasonoftheirfat。Theylivefortwoyears；andthefishermeninferthisagefromthecircumstancethatoncewhentherewasafailureoftheyoungtunnyfishforayeartherewasafailureofthefull-growntunnythenextsummer。Theyareofopinionthatthetunnyisafishayearolderthanthepelamyd。ThetunnyandthemackerelpairaboutthecloseofthemonthofElaphebolion，andspawnaboutthecommencementofthemonthofHecatombaeon；theydeposittheirspawninasortofbag。Thegrowthoftheyoungtunnyisrapid。AfterthefemaleshavespawnedintheEuxine，therecomesfromtheeggwhatsomecallscordylae，butwhattheByzantinesnicknamethe'auxids'or'growers'，fromtheirgrowingtoaconsiderablesizeinafewdays；thesefishgooutofthePontusinautumnalongwiththeyoungtunnies，andenterPontusinthespringaspelamyds。Fishesasaruletakeongrowthwithrapidity，butthisispeculiarlythecasewithallspeciesoffishfoundinthePontus；thegrowth，forinstance，oftheamia-tunnyisquitevisiblefromdaytoday。
Toresume，wemustbearinmindthatthesamefishinthesamelocalitieshavenotthesameseasonforpairing，forconception，forparturition，orforfavouringweather。Thecoracine，forinstance，insomeplacesspawnsaboutwheat-harvest。Thestatementsheregivenpretendonlytogivetheresultsofgeneralobservation。
Thecongeralsospawns，butthefactisnotequallyobviousinalllocalities，noristhespawnplainlyvisibleowingtothefatofthefish；forthespawnislankyinshapeasitiswithserpents。
However，ifitbeputonthefireitshowsitsnature；forthefatevaporatesandmelts，whiletheeggsdanceaboutandexplodewithacrack。Further，ifyoutouchthesubstancesandrubthemwithyourfingers，thefatfeelssmoothandtheeggrough。Somecongersareprovidedwithfatbutnotwithanyspawn，othersareunprovidedwithfatbuthaveegg-spawnasheredescribed。
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Wehave，then，treatedprettyfullyoftheanimalsthatflyintheairorswiminthewater，andofsuchofthosethatwalkondrylandasareoviparous，towitoftheirpairing，conception，andthelikephenomena；itnowremainstotreatofthesamephenomenainconnexionwithviviparouslandanimalsandwithman。
Thestatementsmadeinregardtothepairingofthesexesapplypartlytotheparticularkindsofanimalandpartlytoallingeneral。Itiscommontoallanimalstobemostexcitedbythedesireofonesexfortheotherandbythepleasurederivedfromcopulation。Thefemaleismostcross-temperedjustafterparturition，themaleduringthetimeofpairing；forinstance，stallionsatthisperiodbiteoneanother，throwtheirriders，andchasethem。Wildboars，thoughusuallyenfeebledatthistimeastheresultofcopulation，arenowunusuallyfierce，andfightwithoneanotherinanextraordinaryway，clothingthemselveswithdefensivearmour，orinotherwordsdeliberatelythickeningtheirhidebyrubbingagainsttreesorbycoatingthemselvesrepeatedlyalloverwithmudandthendryingthemselvesinthesun。Theydriveoneanotherawayfromtheswinepastures，andfightwithsuchfurythatveryoftenbothcombatantssuccumb。Thecaseissimilarwithbulls，rams，andhe-goats；for，thoughatordinarytimestheyherdtogether，atbreedingtimetheyholdalooffromandquarrelwithoneanother。Themalecamelalsoiscross-temperedatpairingtimeifeitheramanoracamelcomesnearhim；asforahorse，acamelisreadytofighthimatanytime。Itisthesamewithwildanimals。Thebear，thewolf，andthelionareallatthistimeferocioustowardssuchascomeintheirway，butthemalesoftheseanimalsarelessgiventofightwithoneanotherfromthefactthattheyareatnotimegregarious。Theshe-bearisfierceaftercubbing，andthebitchafterpupping。
Maleelephantsgetsavageaboutpairingtime，andforthisreasonitisstatedthatmenwhohavechargeofelephantsinIndianeverallowthemalestohaveintercoursewiththefemales；onthegroundthatthemalesgowildatthistimeandturntopsy-turvythedwellingsoftheirkeepers，lightlyconstructedastheyare，andcommitallkindsofhavoc。Theyalsostatethatabundancyoffoodhasatendencytotamethemales。Theyfurtherintroduceotherelephantsamongstthewildones，andpunishandbreaktheminbysettingonthenew-comerstochastisetheothers。
Animalsthatpairfrequentlyandnotatasinglespecificseason，asforinstanceanimalsdomesticatedbyman，suchasswineanddogs，arefoundtoindulgeinsuchfreakstoalesserdegreeowingtothefrequencyoftheirsexualintercourse。
Offemaleanimalsthemareisthemostsexuallywanton，andnextinordercomesthecow。Infact，themareissaidtogoa-horsing；andthetermderivedfromthehabitsofthisoneanimalservesasatermofabuseapplicabletosuchfemalesofthehumanspeciesasareunbridledinthewayofsexualappetite。Thisisthecommonphenomenonasobservedinthesowwhensheissaidtogoa-boaring。Themareissaidalsoaboutthistimetogetwind-impregnatedifnotimpregnatedbythestallion，andforthisreasoninCretetheyneverremovethestallionfromthemares；forwhenthemaregetsintothisconditionsherunsawayfromallotherhorses。Themaresunderthesecircumstancesflyinvariablyeithernorthwardsorsouthwards，andnevertowardseithereastorwest。Whenthiscomplaintisonthemtheyallownoonetoapproach，untileithertheyareexhaustedwithfatigueorhavereachedthesea。Undereitherofthesecircumstancestheydischargeacertainsubstance'hippomanes'，thetitlegiventoagrowthonanew-bornfoal；thisresemblesthesow-virus，andisingreatrequestamongstwomenwhodealindrugsandpotions。Abouthorsingtimethemareshuddleclosertogether，arecontinuallyswitchingtheirtails，theirneighisabnormalinsound，andfromthesexualorganthereflowsaliquidresemblinggenitalsperm，butmuchthinnerthanthespermofthemale。Itisthissubstancethatsomecallhippomanes，insteadofthegrowthfoundonthefoal；theysayitisextremelydifficulttogetasitoozesoutonlyinsmalldropsatatime。Maresalso，wheninheat，dischargeurinefrequently，andfriskwithoneanother。Sucharethephenomenaconnectedwiththehorse。
Cowsgoa-bulling；andsocompletelyaretheyundertheinfluenceofthesexualexcitementthattheherdsmenhavenocontroloverthemandcannotcatchholdoftheminthefields。Maresandkinealike，wheninheat，indicatethefactbytheupraisingoftheirgenitalorgans，andbycontinuallyvoidingurine。Further，kinemountthebulls，followthemabout；andkeepstandingbesidethem。Theyoungerfemalesbothwithhorsesandoxenarethefirsttogetinheat；andtheirsexualappetitesareallthekeeneriftheweatherwarmandtheirbodilyconditionbehealthy。Mares，whencliptoftheircoat，havethesexualfeelingchecked，andassumeadowncastdroopingappearance。Thestallionrecognizesbythescentthemaresthatformhiscompany，eventhoughtheyhavebeentogetheronlyafewdaysbeforebreedingtime:iftheygetmixedupwithothermares，thestallionbitesanddrivesawaytheinterlopers。Hefeedsapart，accompaniedbyhisowntroopofmares。Eachstallionhasassignedtohimaboutthirtymaresorevensomewhatmore；whenastrangestallionapproaches，hehuddleshismaresintoaclosering，runsroundthem，thenadvancestotheencounterofthenewcomer；ifoneofthemaresmakeamovement，hebitesheranddrivesherback。
Thebullinbreedingtimebeginstograzewiththecows，andfightswithotherbullshavinghithertograzedwiththem，whichistermedbygraziers'herd-spurning'。OfteninEpirusabulldisappearsforthreemonthstogether。Inageneralwayonemaystatethatofmaleanimalseithernoneorfewherdwiththeirrespectivefemalesbeforebreedingtime；buttheykeepseparateafterreachingmaturity，andthetwosexesfeedapart。Sows，whentheyaremovedbysexualdesire，orare，asitiscalled，a-boaring，willattackevenhumanbeings。
Withbitchesthesamesexualconditionistermed'gettingintoheat'。Thesexualorganrisesatthistime，andthereisamoistureabouttheparts。Maresdripwithawhiteliquidatthisseason。
Femaleanimalsaresubjecttomenstrualdischarges，butneverinsuch-abundanceasisthefemaleofthehumanspecies。Withewesandshe-goatstherearesignsofmenstruationinbreedingtime，justbeforetheforsubmittingtothemale；aftercopulationalsothesignsaremanifest，andthenceaseforanintervaluntiltheperiodofparturitionarrives；theprocessthensupervenes，anditisbythissuperventionthattheshepherdknowsthatsuchandsuchaneweisabouttobringforth。Afterparturitioncomescopiousmenstruation，notatfirstmuchtingedwithblood，butdeeplydyedwithitbyandby。Withthecow，thesheass，andthemare，thedischargeismorecopiousactually，owingtotheirgreaterbulk，butproportionallytothegreaterbulkitisfarlesscopious。Thecow，forinstance，wheninheat，exhibitsasmalldischargetotheextentofaquarterofapintofliquidoralittleless；andthetimewhenthisdischargetakesplaceisthebesttimeforhertobecoveredbythebull。Ofallquadrupedsthemareisthemosteasilydeliveredofitsyoung，exhibitstheleastamountofdischargeafterparturition，andemitstheleastamountofblood；thatistosay，ofallanimalsinproportiontosize。Withkineandmaresmenstruationusuallymanifestsitselfatintervalsoftwo，four，andsixmonths；but，unlessonebeconstantlyattendingtoandthoroughlyacquaintedwithsuchanimals，itisdifficulttoverifythecircumstance，andtheresultisthatmanypeopleareunderthebeliefthattheprocessnevertakesplacewiththeseanimalsatall。
Withmulesmenstruationnevertakesplace，buttheurineofthefemaleisthickerthantheurineofthemale。Asageneralrulethedischargefromthebladderinthecaseofquadrupedsisthickerthanitisinthehumanspecies，andthisdischargewithewesandshe-goatsisthickerthanwithramsandhe-goats；buttheurineofthejackassisthickerthantheurineoftheshe-ass，andtheurineofthebullismorepungentthantheurineofthecow。Afterparturitiontheurineofallquadrupedsbecomesthicker，especiallywithsuchanimalsasexhibitcomparativelyslightdischarges。Atbreedingtimethemilkbecomepurulent，butafterparturitionitbecomeswholesome。Duringpregnancyewesandshe-goatsgetfatterandeatmore；asisalsothecasewithcows，and，indeed，withthefemalesofallquadrupeds。
Ingeneralthesexualappetitesofanimalsarekeenestinspring-time；thetimeofpairing，however，isnotthesameforall，butisadaptedsoastoensuretherearingoftheyoungataconvenientseason。
Domesticatedswinecarrytheiryoungforfourmonths，andbringforthalitteroftwentyattheutmost；and，bytheway，ifthelitterbeexceedinglynumeroustheycannotrearalltheyoung。
Asthesowgrowsoldshecontinuestobear，butgrowsindifferenttotheboar；sheconceivesafterasinglecopulation，buttheyhavetoputtheboartoherrepeatedlyowingtoherdroppingafterintercoursewhatiscalledthesow-virus。Thisincidentbefallsallsows，butsomeofthemdischargethegenitalspermaswell。Duringconceptionanyoneofthelitterthatgetsinjuredordwarfediscalledanafterpigorscut:suchinjurymayoccuratanypartofthewomb。Afterlitteringthemotherofferstheforemostteattothefirst-born。Whenthesowisinheat，shemustnotatoncebeputtotheboar，butonlyaftersheletsherlugsdrop，forotherwisesheisapttogetintoheatagain；
ifshebeputtotheboarwheninfullconditionofheat，onecopulation，ashasbeensaid，issufficient。Itisaswelltosupplytheboarattheperiodofcopulationwithbarley，andthesowatthetimeofparturitionwithboiledbarley。Someswinegivefinelittersonlyatthebeginning，withothersthelittersimproveasthemothersgrowinageandsize。Itissaidthatasow，ifshehaveoneofhereyesknockedout，isalmostsuretodiesoonafterwards。
Swineforthemostpartliveforfifteenyears，butsomefalllittleshortofthetwenty。