▁the ▁first ▁instance , ▁and ▁which , ▁in ▁many ▁cases , ▁was ▁un att ain able ▁by ▁ordinary ▁means , ▁particular ▁species ▁have ▁therefore ▁been ▁so ▁organized ▁( that ▁is ▁to ▁say , ▁modified ▁upon ▁some ▁more ▁or ▁less ▁general ▁type ▁or ▁plan ▁of ▁structure , ) ▁to ▁avail ▁themselves ▁of ▁the ▁supply ." ▁ ▁Stephen ▁Jay ▁G ould ▁writes ▁that ▁E ise ley ▁er red ▁in ▁failing ▁to ▁realize ▁that ▁natural ▁selection ▁was ▁a ▁common ▁idea ▁among ▁bi olog ists ▁of ▁the ▁time , ▁as ▁part ▁of ▁the ▁argument ▁for ▁created ▁perman ency ▁of ▁species . ▁It ▁was ▁seen ▁as ▁elimin ating ▁the ▁un fit , ▁while ▁some ▁other ▁cause ▁created ▁well - f itted ▁species . ▁Dar win ▁introduced ▁the ▁idea ▁that ▁natural ▁selection ▁was ▁cre ative ▁in ▁giving ▁direction ▁to ▁a ▁process ▁of ▁evolution ary ▁change ▁in ▁which ▁small ▁her edit ary ▁changes ▁accum ulate . ▁John ▁Wil kins ▁indicates ▁that ▁B ly th ▁considered ▁that ▁species ▁had ▁" in variable ▁dist in ctions " ▁establish ing ▁their ▁integrity , ▁and ▁so ▁was ▁opposed ▁to ▁trans mut ation ▁of ▁species ▁as ▁if ▁it ▁occurred , ▁" we ▁should ▁seek ▁in ▁vain ▁for ▁those ▁constant ▁and ▁invari able ▁dist in ctions ▁which ▁are ▁found ▁to ▁obtain ". ▁Dar win ▁held ▁the ▁opposite ▁view , ▁and ▁did ▁not ▁read ▁B ly th ▁until ▁after ▁form ulating ▁his ▁own ▁theory . ▁In ▁contrast ▁to ▁E ise ley ' s ▁claim ▁that ▁B ly th ▁felt ▁that ▁Dar win ▁had ▁pl ag iar ised