The acquisition of a useless part can hardly be said to raise an organism in the natural scale; and in the case of the imperfect, closed flowers, above described, if any new principle has to be invoked, it must be one of retrogression rather than of progression; and so it must be with many parasitic and degraded animals.
Nekez esan daiteke organismo batek baliagarri ez duen atal bat bereganatzeak, natur eskalan gorago jartzen duenik, eta arestian deskribaturiko lore itxi hobagarrien kasuan, hastapen berriren bat inbokatu ezean, aurrerakuntzako kasua barik gibelamendukoa izan daiteke; eta gauza bera esan behar da animalia bizkarroi eta degradatu askori dagokienez.