Havingnowendeavouredtoshowthattheseveralforegoingassumptionsaretoacertainextentsupportedbyanalogousfacts，andhavingalludedtosomeofthemostdoubtfulpoints，wewillconsiderhowfarthehypothesisbringsunderasinglepointofviewthevariouscasesenumeratedintheFirstPart。Alltheformsofreproductiongraduateintooneanotherandagreeintheirproduct;
foritisimpossibletodistinguishbetweenorganismsproducedfrombuds，fromself—division，orfromfertilisedgerms;suchorganismsareliabletovariationsofthesamenatureandtoreversionsofthesamekind;andas，accordingtoourhypothesis，alltheformsofreproductiondependontheaggregationofgemmulesderivedfromthewholebody，wecanunderstandthisremarkableagreement。Parthenogenesisisnolongerwonderful，andifwedidnotknowthatgreatgoodfollowedfromtheunionofthesexualelementsderivedfromtwodistinctindividuals，thewonderwouldbethatparthenogenesisdidnotoccurmuchoftenerthanitdoes。Onanyordinarytheoryofreproductiontheformationofgraft—hybrids，andtheactionofthemaleelementonthetissuesofthemother—plant，aswellasonthefutureprogenyoffemaleanimals，aregreatanomalies;buttheyareintelligibleonourhypothesis。Thereproductiveorgansdonotactuallycreatethesexualelements;theymerelydeterminetheaggregationandperhapsthemultiplicationofthegemmulesinaspecialmanner。Theseorgans，however，togetherwiththeiraccessoryparts，havehighfunctionstoperform。Theyadaptoneorbothelementsforindependenttemporaryexistence，andformutualunion。Thestigmaticsecretionactsonthepollenofaplantofthesamespeciesinawhollydifferentmannertowhatitdoesonthepollenofonebelongingtoadistinctgenusorfamily。ThespermatophoresoftheCephalopodaarewonderfullycomplexstructures，whichwereformerlymistakenforparasiticworms;andthespermatozoaofsomeanimalspossessattributeswhich，ifobservedinanindependentanimal，wouldbeputdowntoinstinctguidedbysense—organs，——aswhenthespermatozoaofaninsectfindtheirwayintotheminutemicropyleoftheegg。
Theantagonismwhichhaslongbeenobserved（27/55。Mr。HerbertSpencer（’PrinciplesofBiology’volume2page430）hasfullydiscussedthisantagonism。），withcertainexceptions，betweengrowthandthepowerofsexualreproduction（27/56。Themalesalmonisknowntobreedataveryearlyage。
TheTritonandSiredon，whilstretainingtheirlarvalbranchiae，accordingtoFilippiandDumeril（’AnnalsandMag。ofNat。Hist。’3rdseries1866page157）
arecapableofreproduction。ErnstHaeckelhasrecently（’MonatsberichtAkad。