variable。PartofthedifferencewithplantsmaybeaccountedforbymanyofmycasesbeingsecondarymaleorFEMALEcharacters，butthenIhavestrikingcaseswithhermaphroditeCirripedes。Thecasesseemtomefartoonumerousforaccidentalcoincidences，ofgreatvariabilityandabnormaldevelopment。Ipresumethatyouwillnotobjecttomyputtinganotesayingthatyouhadreflectedoverthecase，andthoughoneortwocasesseemedtosupport，quiteasmanyormoreseemedwhollycontradictory。Thiswantofevidenceisthemoresurprisingtome，asgenerallyIfindanypropositionmoreeasilytestedbyobservationsinbotanicalworks，whichI
havepickedup，thaninzoologicalworks。Ineverdreamedthatyouhadkeptthesubjectatallbeforeyourmind。AltogetherthecaseisonemoreofmyMANYhorridpuzzles。Myobservations，thoughonsoinfinitelyasmallscale，onthestruggleforexistence，begintomakemeseealittleclearerhowthefightgoeson。Outofsixteenkindsofseedsownonmymeadow，fifteenhavegerminated，butnowtheyareperishingatsucharatethatIdoubtwhethermorethanonewillflower。Herewehavechokingwhichhastakenplacelikewiseonagreatscale，withplantsnotseedlings，inabitofmylawnallowedtogrowup。Ontheotherhand，inabitofground，2by3feet，IhavedailymarkedeachseedlingweedasithasappearedduringMarch，AprilandMay，and357havecomeup，andofthese277haveALREADYbeenkilledchieflybyslugs。Bytheway，atMoorPark，Isawratheraprettycaseoftheeffectsofanimalsonvegetation:thereareenormouscommonswithclumpsofoldScotchfirsonthehills，andabouteightortenyearsagosomeofthesecommonswereenclosed，andallroundtheclumpsniceyoungtreesarespringingupbythemillion，lookingexactlyasifplanted，somanyareofthesameage。Inotherpartsofthecommon，notyetenclosed，IlookedformilesandnotONEyoungtreecouldbeseen。Ithenwentnear（withinquarterofamileoftheclumps）andlookedcloselyintheheather，andthereIfoundtensofthousandsofyoungScotchfirs（thirtyinonesquareyard）withtheirtopsnibbledoffbythefewcattlewhichoccasionallyroamoverthesewretchedheaths。Onelittletree，threeincheshigh，bytheringsappearedtobetwenty—sixyearsold，withashortstemaboutasthickasastickofsealing—wax。Whatawondrousproblemitis，whataplayofforces，determiningthekindandproportionofeachplantinasquareyardofturf！Itistomymindtrulywonderful。Andyetwearepleasedtowonderwhensomeanimalorplantbecomesextinct。
IamsosorrythatyouwillnotbeattheClub。IseeMrs。HookerisgoingtoYarmouth;Itrustthatthehealthofyourchildrenisnotthemotive。
Good—bye。
MydearHooker，everyours，C。DARWIN。