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1、PassageThirteen(CrypticColoring)Crypticcoloringisbyfarthecommonestuseofcolorinthestruggleforexistence.Itisemployedforthepurposeofattack(aggressiveresemblanceoranticrypticcoloring)aswellasofdefense(protectiveresemblanceorprocrypticcoloring).Thefactthatt
2、hesamemethodconcealment,maybeusedbothforattackanddefensehasbeenwellexplainedbyT.Beltwhosuggestsasanillustrationtherapidityofmovementwhichisalsomadeuseofbybothpursuerandpursued,whichissimilarlyraisedtoamaximuminbothbythegradualdyingoutoftheslowestthroug
3、haseriesofgenerations.Crypticcoloringiscommonlyassociatedwithotheraidsinthestruggleforlife.Thuswell-concealedmammalsandbirds,whendiscovered,willgenerallyendeavortoescapebyspeedandwilloftenattempttodefendthemselvesactively.Ontheotherhand,smallanimalswhi
4、chhavenomeansofactivedefense,suchaslarge,numbersofinsects,frequentlydependuponconcealmentalone.Protectiveresemblanceisfarcommoneramonganimalsthanaggressiveresemblance,incorrespondencewiththefactthatpredaceousformsareasarulemuchlargerandmuchlessnumerous
5、thantheirprey.InthecaseofinsectivorousVertebrataandtheirpreysuchdifferencesexistinanexaggeratedform.Crypticcoloring,whetherusedfordefenseofattack,maybeeithergeneralorspecial.Ingeneralresemblancetheanimal,inconsequenceofitscoloring,producesthesameeffect
6、asitsenvironment,buttheconditionsdonotrequireanyspecialadaptationofshapeandoutline.Generalresemblanceisespeciallycommonamongtheanimalinhabitingsomeuniformlycoloredexpanseoftheearth’ssurface,suchasanoceanoradesert.Intheformer,animalsofallshapesarefreque
7、ntlyprotectedbytheirtransparentbluecolor,onthelatter,equallydiverseformsaredefendedbytheirsandyappearance.Theeffectofauniformappearancemaybeproducedbyacombinationoftintsinstartlingcontrast.Thustheblackandwhitestripesofthezebrablendtogetheratalittledist
8、ance,and“theirproportionissuchasexactlytomatchthepaletintwhicharidgroundpossesseswhenseenbymoonlight.”Specialresemblanceisfarcommonerthangeneralandistheformwhichisusuallymetwithonthediversifiedsurfaceoftheearth,ontheshores,andinshalloww
