The Foundations of the Origin of Species

abortive according acquired adapted admit ages America animals appear become believe birds breed cause certain changes chapter character climate closely common compared consider continent course crossing descended developed difficulty distinct distribution divisions dogs domestic doubt effect embryo evidence existing explained external extinct facts families favourable follow formation forms fossil genera give greater groups habits importance increase individuals inhabitants inherited instance instincts intermediate islands kind known land latter laws less living look manner means mountains namely naturalists nature nearly observed occasionally offspring organisms Origin parent perhaps period plants points possible present preserved probably produced races reason remain remarked resemble respect seeds seems selection separate shown similar slight species sterility structure suppose tend theory true variation varieties vary whole widely wild wonderful young