On the other hand, the fact that instincts are not always absolutely perfect and are liable to mistakes; that no instinct can be shown to have been produced for the good of other animals, though animals take advantage of the instincts of others; that the canon in natural history, of "Natura non facit saltum," is applicable to instincts as well as to corporeal structure, and is plainly explicable on the foregoing views, but is otherwise inexplicable-all tend to corroborate the theory of natural selection.
Aitzitik, instintuak beti erabat hobezinak ez izatea eta errakuntzaren mende egotea, beste animalia batzuen onerako sortua den instintu bat bera ere denik frogatzeko modurik ez izatea, animaliek beste animalia batzuen instintuetatik onura jaso arren, "Natura non facit saltum" natur historiako araua instintuei zein gorputz egiturari aplikagarria izatea eta aurreko teorien arabera argiro azaltzea, baina bestela azalezina izatea, horiek guztiok hautespen naturalaren teoria berrestera datoz.