Finally, then, although in many cases it is most difficult even to conjecture by what transitions organs could have arrived at their present state; yet, considering how small the proportion of living and known forms is to the extinct and unknown, I have been astonished how rarely an organ can be named, towards which no transitional grade is known to lead.
Azkenez, bada, kasu askotan zer nolako iragaitzetatik pasa behar izan duten organoek egungo egoerara heltzeko antzematea oso zaila den arren, hala ere, kontuan izanik zein txikia den bizi diren eta ezagutzen ditugun formen proportzioa, iraungi diren eta ezagutzen ez ditugunekin konparaturik, harritu egin nau ikusteak zein bakanki aipa daitekeen haietara heltzeko iragaitza mailarik ezagutzen ez zaion organoren bat.