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There¡¡are¡¡other¡¡relations¡¡between¡¡the¡¡species¡¡of¡¡large¡¡genera¡¡and¡¡their¡¡recorded¡¡varieties¡¡which¡¡deserve¡¡notice¡£¡¡We¡¡have¡¡seen¡¡that¡¡there¡¡is¡¡no¡¡infallible¡¡criterion¡¡by¡¡which¡¡to¡¡distinguish¡¡species¡¡and¡¡well¡­marked¡¡varieties£»¡¡and¡¡in¡¡those¡¡cases¡¡in¡¡which¡¡intermediate¡¡links¡¡have¡¡not¡¡been¡¡found¡¡between¡¡doubtful¡¡forms£»¡¡naturalists¡¡are¡¡compelled¡¡to¡¡come¡¡to¡¡a¡¡determination¡¡by¡¡the¡¡amount¡¡of¡¡difference¡¡between¡¡them£»¡¡judging¡¡by¡¡analogy¡¡whether¡¡or¡¡not¡¡the¡¡amount¡¡suffices¡¡to¡¡raise¡¡one¡¡or¡¡both¡¡to¡¡the¡¡rank¡¡of¡¡species¡£¡¡Hence¡¡the¡¡amount¡¡of¡¡difference¡¡is¡¡one¡¡very¡¡important¡¡criterion¡¡in¡¡settling¡¡whether¡¡two¡¡forms¡¡should¡¡be¡¡ranked¡¡as¡¡species¡¡or¡¡varieties¡£¡¡Now¡¡Fries¡¡has¡¡remarked¡¡in¡¡regard¡¡to¡¡plants£»¡¡and¡¡Westwood¡¡in¡¡regard¡¡to¡¡insects£»¡¡that¡¡in¡¡large¡¡genera¡¡the¡¡amount¡¡of¡¡difference¡¡between¡¡the¡¡species¡¡is¡¡often¡¡exceedingly¡¡small¡£¡¡I¡¡have¡¡endeavoured¡¡to¡¡test¡¡this¡¡numerically¡¡by¡¡averages£»¡¡and£»¡¡as¡¡far¡¡as¡¡my¡¡imperfect¡¡results¡¡go£»¡¡they¡¡always¡¡confirm¡¡the¡¡view¡£¡¡I¡¡have¡¡also¡¡consulted¡¡some¡¡sagacious¡¡and¡¡most¡¡experienced¡¡observers£»¡¡and£»¡¡after¡¡deliberation£»¡¡they¡¡concur¡¡in¡¡this¡¡view¡£¡¡In¡¡this¡¡respect£»¡¡therefore£»¡¡the¡¡species¡¡of¡¡the¡¡larger¡¡genera¡¡resemble¡¡varieties£»¡¡more¡¡than¡¡do¡¡the¡¡species¡¡of¡¡the¡¡smaller¡¡genera¡£¡¡Or¡¡the¡¡case¡¡may¡¡be¡¡put¡¡in¡¡another¡¡way£»¡¡and¡¡it¡¡may¡¡be¡¡said£»¡¡that¡¡in¡¡the¡¡larger¡¡genera£»¡¡in¡¡which¡¡a¡¡number¡¡of¡¡varieties¡¡or¡¡incipient¡¡species¡¡greater¡¡than¡¡the¡¡average¡¡are¡¡now¡¡manufacturing£»¡¡many¡¡of¡¡the¡¡species¡¡already¡¡manufactured¡¡still¡¡to¡¡a¡¡certain¡¡extent¡¡resemble¡¡varieties£»¡¡for¡¡they¡¡differ¡¡from¡¡each¡¡other¡¡by¡¡a¡¡less¡¡than¡¡usual¡¡amount¡¡of¡¡difference¡£¡¡
Moreover£»¡¡the¡¡species¡¡of¡¡the¡¡large¡¡genera¡¡are¡¡related¡¡to¡¡each¡¡other£»¡¡in¡¡the¡¡same¡¡manner¡¡as¡¡the¡¡varieties¡¡of¡¡any¡¡one¡¡species¡¡are¡¡related¡¡to¡¡each¡¡other¡£¡¡No¡¡naturalist¡¡pretends¡¡that¡¡all¡¡the¡¡species¡¡of¡¡a¡¡genus¡¡are¡¡equally¡¡distinct¡¡from¡¡each¡¡other£»¡¡they¡¡may¡¡generally¡¡be¡¡divided¡¡into¡¡sub¡­genera£»¡¡or¡¡sections£»¡¡or¡¡lesser¡¡groups¡£¡¡As¡¡Fries¡¡has¡¡well¡¡remarked£»¡¡little¡¡groups¡¡of¡¡species¡¡are¡¡generally¡¡clustered¡¡like¡¡satellites¡¡around¡¡certain¡¡other¡¡species¡£¡¡And¡¡what¡¡are¡¡varieties¡¡but¡¡groups¡¡of¡¡forms£»¡¡unequally¡¡related¡¡to¡¡each¡¡other£»¡¡and¡¡clustered¡¡round¡¡certain¡¡forms¡¡that¡¡is£»¡¡round¡¡their¡¡parent¡­species£¿¡¡Undoubtedly¡¡there¡¡is¡¡one¡¡most¡¡important¡¡point¡¡of¡¡difference¡¡between¡¡varieties¡¡and¡¡species£»¡¡namely£»¡¡that¡¡the¡¡amount¡¡of¡¡difference¡¡between¡¡varieties£»¡¡when¡¡compared¡¡with¡¡each¡¡other¡¡or¡¡with¡¡their¡¡parent¡­species£»¡¡is¡¡much¡¡less¡¡than¡¡that¡¡between¡¡the¡¡species¡¡of¡¡the¡¡same¡¡genus¡£¡¡But¡¡when¡¡we¡¡come¡¡to¡¡discuss¡¡the¡¡principle£»¡¡as¡¡I¡¡call¡¡it£»¡¡of¡¡Divergence¡¡of¡¡Character£»¡¡we¡¡shall¡¡see¡¡how¡¡this¡¡may¡¡be¡¡explained£»¡¡and¡¡how¡¡the¡¡lesser¡¡differences¡¡between¡¡varieties¡¡will¡¡tend¡¡to¡¡increase¡¡into¡¡the¡¡greater¡¡differences¡¡between¡¡species¡£¡¡
There¡¡is¡¡one¡¡other¡¡point¡¡which¡¡seems¡¡to¡¡me¡¡worth¡¡notice¡£¡¡Varieties¡¡generally¡¡have¡¡much¡¡restricted¡¡ranges£º¡¡this¡¡statement¡¡is¡¡indeed¡¡scarcely¡¡more¡¡than¡¡a¡¡truism£»¡¡for¡¡if¡¡a¡¡variety¡¡were¡¡found¡¡to¡¡have¡¡a¡¡wider¡¡range¡¡than¡¡that¡¡of¡¡its¡¡supposed¡¡parent¡­species£»¡¡their¡¡denominations¡¡ought¡¡to¡¡be¡¡reversed¡£¡¡But¡¡there¡¡is¡¡also¡¡reason¡¡to¡¡believe£»¡¡that¡¡those¡¡species¡¡which¡¡are¡¡very¡¡closely¡¡allied¡¡to¡¡other¡¡species£»¡¡and¡¡in¡¡so¡¡far¡¡resemble¡¡varieties£»¡¡often¡¡have¡¡much¡¡restricted¡¡ranges¡£¡¡For¡¡instance£»¡¡Mr¡¡H¡£¡¡C¡£¡¡Watson¡¡has¡¡marked¡¡for¡¡me¡¡in¡¡the¡¡well¡­sifted¡¡London¡¡Catalogue¡¡of¡¡plants¡¡£¨4th¡¡edition£©¡¡63¡¡plants¡¡which¡¡are¡¡therein¡¡ranked¡¡as¡¡species£»¡¡but¡¡which¡¡he¡¡considers¡¡as¡¡so¡¡closely¡¡allied¡¡to¡¡other¡¡species¡¡as¡¡to¡¡be¡¡of¡¡doubtful¡¡value£º¡¡these¡¡63¡¡reputed¡¡species¡¡range¡¡on¡¡an¡¡average¡¡over¡¡6¡£9¡¡of¡¡the¡¡provinces¡¡into¡¡which¡¡Mr¡¡Watson¡¡has¡¡divided¡¡Great¡¡Britain¡£¡¡Now£»¡¡in¡¡this¡¡same¡¡catalogue£»¡¡53¡¡acknowledged¡¡varieties¡¡are¡¡recorded£»¡¡and¡¡these¡¡range¡¡over¡¡7¡£7¡¡provinces£»¡¡whereas£»¡¡the¡¡species¡¡to¡¡which¡¡these¡¡varieties¡¡belong¡¡range¡¡over¡¡14¡£3¡¡provinces¡£¡¡So¡¡that¡¡the¡¡acknowledged¡¡varieties¡¡have¡¡very¡¡nearly¡¡the¡¡same¡¡restricted¡¡average¡¡range£»¡¡as¡¡have¡¡those¡¡very¡¡closely¡¡allied¡¡forms£»¡¡marked¡¡for¡¡me¡¡by¡¡Mr¡¡Watson¡¡as¡¡doubtful¡¡species£»¡¡but¡¡which¡¡are¡¡almost¡¡universally¡¡ranked¡¡by¡¡British¡¡botanists¡¡as¡¡good¡¡and¡¡true¡¡species¡£¡¡
Finally£»¡¡then£»¡¡varieties¡¡have¡¡the¡¡same¡¡general¡¡characters¡¡as¡¡species£»¡¡for¡¡they¡¡cannot¡¡be¡¡distinguished¡¡from¡¡species£»¡¡except£»¡¡firstly£»¡¡by¡¡the¡¡discovery¡¡of¡¡intermediate¡¡linking¡¡forms£»¡¡and¡¡the¡¡occurrence¡¡of¡¡such¡¡links¡¡cannot¡¡affect¡¡the¡¡actual¡¡characters¡¡of¡¡the¡¡forms¡¡which¡¡they¡¡connect£»¡¡and¡¡except£»¡¡secondly£»¡¡by¡¡a¡¡certain¡¡amount¡¡of¡¡difference£»¡¡for¡¡two¡¡forms£»¡¡if¡¡differing¡¡very¡¡little£»¡¡are¡¡generally¡¡ranked¡¡as¡¡varieties£»¡¡notwithstanding¡¡that¡¡intermediate¡¡linking¡¡forms¡¡have¡¡not¡¡been¡¡discovered£»¡¡but¡¡the¡¡amount¡¡of¡¡difference¡¡considered¡¡necessary¡¡to¡¡give¡¡to¡¡two¡¡forms¡¡the¡¡rank¡¡of¡¡species¡¡is¡¡quite¡¡indefinite¡£¡¡In¡¡genera¡¡having¡¡more¡¡than¡¡the¡¡average¡¡number¡¡of¡¡species¡¡in¡¡any¡¡country£»¡¡the¡¡species¡¡of¡¡these¡¡genera¡¡have¡¡more¡¡than¡¡the¡¡average¡¡number¡¡of¡¡varieties¡£¡¡In¡¡large¡¡genera¡¡the¡¡species¡¡are¡¡apt¡¡to¡¡be¡¡closely£»¡¡but¡¡unequally£»¡¡allied¡¡together£»¡¡forming¡¡little¡¡clusters¡¡round¡¡certain¡¡species¡£¡¡Species¡¡very¡¡closely¡¡allied¡¡to¡¡other¡¡species¡¡apparently¡¡have¡¡restricted¡¡ranges¡£¡¡In¡¡all¡¡these¡¡several¡¡respects¡¡the¡¡species¡¡of¡¡large¡¡genera¡¡present¡¡a¡¡strong¡¡analogy¡¡with¡¡varieties¡£¡¡And¡¡we¡¡can¡¡clearly¡¡understand¡¡these¡¡analogies£»¡¡if¡¡species¡¡have¡¡once¡¡existed¡¡as¡¡varieties£»¡¡and¡¡have¡¡thus¡¡originated£º¡¡whereas£»¡¡these¡¡analogies¡¡are¡¡utterly¡¡inexplicable¡¡if¡¡each¡¡species¡¡has¡¡been¡¡independently¡¡created¡£¡¡
We¡¡have£»¡¡also£»¡¡seen¡¡that¡¡it¡¡is¡¡the¡¡most¡¡flourishing¡¡and¡¡dominant¡¡species¡¡of¡¡the¡¡larger¡¡genera¡¡which¡¡on¡¡an¡¡average¡¡vary¡¡most£»¡¡and¡¡varieties£»¡¡as¡¡we¡¡shall¡¡hereafter¡¡see£»¡¡tend¡¡to¡¡become¡¡converted¡¡into¡¡new¡¡and¡¡distinct¡¡species¡£¡¡The¡¡larger¡¡genera¡¡thus¡¡tend¡¡to¡¡become¡¡larger£»¡¡and¡¡throughout¡¡nature¡¡the¡¡forms¡¡of¡¡life¡¡which¡¡are¡¡now¡¡dominant¡¡tend¡¡to¡¡become¡¡still¡¡more¡¡dominant¡¡by¡¡leaving¡¡many¡¡modified¡¡and¡¡dominant¡¡descendants¡£¡¡But¡¡by¡¡steps¡¡hereafter¡¡to¡¡be¡¡explained£»¡¡the¡¡larger¡¡genera¡¡also¡¡tend¡¡to¡¡break¡¡up¡¡into¡¡smaller¡¡genera¡£¡¡And¡¡thus£»¡¡the¡¡forms¡¡of¡¡life¡¡throughout¡¡the¡¡universe¡¡become¡¡divided¡¡into¡¡groups¡¡subordinate¡¡to¡¡groups¡£¡¡¡¡
The¡¡Origin¡¡of¡¡Species
by¡¡Charles¡¡Darwin

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Chapter¡¡3¡¡¡­¡¡Struggle¡¡for¡¡Existence

BEF0RE¡¡entering¡¡on¡¡the¡¡subject¡¡of¡¡this¡¡chapter£»¡¡I¡¡must¡¡make¡¡a¡¡few¡¡preliminary¡¡remarks£»¡¡to¡¡show¡¡how¡¡the¡¡struggle¡¡for¡¡existence¡¡bears¡¡on¡¡Natural¡¡Selection¡£¡¡It¡¡has¡¡been¡¡seen¡¡in¡¡the¡¡last¡¡chapter¡¡that¡¡amongst¡¡organic¡¡beings¡¡in¡¡a¡¡state¡¡of¡¡nature¡¡there¡¡is¡¡some¡¡individual¡¡variability£»¡¡indeed¡¡I¡¡am¡¡not¡¡aware¡¡that¡¡this¡¡has¡¡ever¡¡been¡¡disputed¡£¡¡It¡¡is¡¡immaterial¡¡for¡¡us¡¡whether¡¡a¡¡multitude¡¡of¡¡doubtful¡¡forms¡¡be¡¡called¡¡species¡¡or¡¡sub¡­species¡¡or¡¡varieties£»¡¡what¡¡rank£»¡¡for¡¡instance£»¡¡the¡¡two¡¡or¡¡three¡¡hundred¡¡doubtful¡¡forms¡¡of¡¡British¡¡plants¡¡are¡¡entitled¡¡to¡¡hold£»¡¡if¡¡the¡¡existence¡¡of¡¡any¡¡well¡­marked¡¡varieties¡¡be¡¡admitted¡£¡¡But¡¡the¡¡mere¡¡existence¡¡of¡¡individual¡¡variability¡¡and¡¡of¡¡some¡¡few¡¡well¡­marked¡¡varieties£»¡¡though¡¡necessary¡¡as¡¡the¡¡foundation¡¡for¡¡the¡¡work£»¡¡helps¡¡us¡¡but¡¡little¡¡in¡¡understanding¡¡how¡¡species¡¡arise¡¡in¡¡nature¡£¡¡How¡¡have¡¡all¡¡those¡¡exquisite¡¡adaptations¡¡of¡¡one¡¡part¡¡of¡¡the¡¡organisation¡¡to¡¡another¡¡part£»¡¡and¡¡to¡¡the¡¡conditions¡¡of¡¡life£»¡¡and¡¡of¡¡one¡¡distinct¡¡organic¡¡being¡¡to¡¡another¡¡being£»¡¡been¡¡perfected£¿¡¡We¡¡see¡¡these¡¡beautiful¡¡co¡­adaptations¡¡most¡¡plainly¡¡in¡¡the¡¡woodpecker¡¡and¡¡missletoe£»¡¡and¡¡only¡¡a¡¡little¡¡less¡¡plainly¡¡in¡¡the¡¡humblest¡¡parasite¡¡which¡¡clings¡¡to¡¡the¡¡hairs¡¡of¡¡a¡¡quadruped¡¡or¡¡feathers¡¡of¡¡a¡¡bird£»¡¡in¡¡the¡¡structure¡¡of¡¡the¡¡beetle¡¡which¡¡dives¡¡through¡¡the¡¡water£»¡¡in¡¡the¡¡plumed¡¡seed¡¡which¡¡is¡¡wafted¡¡by¡¡the¡¡gentlest¡¡breeze£»¡¡in¡¡short£»¡¡we¡¡see¡¡beautiful¡¡adaptations¡¡everywhere¡¡and¡¡in¡¡every¡¡part¡¡of¡¡the¡¡organic¡¡world¡£¡¡
Again£»¡¡it¡¡may¡¡be¡¡asked£»¡¡how¡¡is¡¡it¡¡that¡¡varieties£»¡¡which¡¡I¡¡have¡¡called¡¡incipient¡¡species£»¡¡become¡¡ultimately¡¡converted¡¡into¡¡good¡¡and¡¡distinct¡¡species£»¡¡which¡¡in¡¡most¡¡cases¡¡obviously¡¡differ¡¡from¡¡each¡¡other¡¡far¡¡more¡¡than¡¡do¡¡the¡¡varieties¡¡of¡¡the¡¡same¡¡species£¿¡¡How¡¡do¡¡those¡¡groups¡¡of¡¡species£»¡¡which¡¡constitute¡¡what¡¡are¡¡called¡¡distinct¡¡genera£»¡¡and¡¡which¡¡differ¡¡from¡¡each¡¡other¡¡more¡¡than¡¡do¡¡the¡¡species¡¡of¡¡the¡¡same¡¡genus£»¡¡arise£¿¡¡All¡¡these¡¡results£»¡¡as¡¡we¡¡shall¡¡more¡¡fully¡¡see¡¡in¡¡the¡¡next¡¡chapter£»¡¡follow¡¡inevitably¡¡from¡¡the¡¡struggle¡¡for¡¡life¡£¡¡Owing¡¡to¡¡this¡¡struggle¡¡for¡¡life£»¡¡any¡¡variation£»¡¡however¡¡slight¡¡and¡¡from¡¡whatever¡¡cause¡¡proceeding£»¡¡if¡¡it¡¡be¡¡in¡¡any¡¡degree¡¡profitable¡¡to¡¡an¡¡individual¡¡of¡¡any¡¡species£»¡¡in¡¡its¡¡infinitely¡¡complex¡¡relations¡¡to¡¡other¡¡organic¡¡beings¡¡and¡¡to¡¡external¡¡nature£»¡¡will¡¡tend¡¡to¡¡the¡¡preservation¡¡of¡¡that¡¡individual£»¡¡and¡¡will¡¡generally¡¡be¡¡inherited¡¡by¡¡its¡¡offspring¡£¡¡The¡¡offspring£»¡¡also£»¡¡will¡¡thus¡¡have¡¡a¡¡better¡¡chance¡¡of¡¡surviving£»¡¡for£»¡¡of¡¡the¡¡many¡¡individuals¡¡of¡¡any¡¡species¡¡which¡¡are¡¡periodically¡¡born£»¡¡but¡¡a¡¡small¡¡number¡¡can¡¡survive¡£¡¡I¡¡have¡¡called¡¡this¡¡principle£»¡¡by¡¡which¡¡each¡¡slight¡¡variation£»¡¡if¡¡useful£»¡¡is¡¡preserved£»¡¡by¡¡the¡¡term¡¡of¡¡Natural¡¡Selection£»¡¡in¡¡order¡¡to¡¡mark¡¡its¡¡relation¡¡to¡¡man's¡¡power¡¡of¡¡selection¡£¡¡We¡¡have¡¡seen¡¡that¡¡man¡¡by¡¡selection¡¡can¡¡certainly¡¡produce¡¡great¡¡results£»¡¡and¡¡can¡¡adapt¡¡organic¡¡beings¡¡to¡¡his¡¡own¡¡uses£»¡¡through¡¡the¡¡accumulation¡¡of¡¡slight¡¡but¡¡useful¡¡variations£»¡¡given¡¡to¡¡him¡¡by¡¡the¡¡hand¡¡of¡¡Nature¡£¡¡But¡¡Natural¡¡Selection£»¡¡as¡¡we¡¡shall¡¡hereafter¡¡see£»¡¡is¡¡a¡¡power¡¡incessantly¡¡ready¡¡for¡¡action£»¡¡and¡¡is¡¡as¡¡immeasurably¡¡superior¡¡to¡¡man's¡¡feeble¡¡efforts£»¡¡as¡¡the¡¡works¡¡of¡¡Nature¡¡ar

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