That the mere physiological importance of an organ does not determine its classificatory value, is almost proved by the fact, that in allied groups, in which the same organ, as we have every reason to suppose, has nearly the same physiological value, its classificatory value is widely different.
Organo baten garrantzi fisiologiko hutsa ez dela aski haren sailkapen-balioa ebazteko, ondoko egitate honexek frogatzen digu ia: talde ahaideetan balio fisiologiko berdintsua duen organo berak, eta horrelakoa duela uste izateko arrazoi asko dugu, sailkatzeko balio arras ezberdina izateak.