To compare small things with great; if the principal living and extinct races of the domestic pigeon were arranged in serial affinity, this arrangement would not closely accord with the order in time of their production, and even less with the order of their disappearance; for the parent rock-pigeon still lives; and many varieties between the rock-pigeon and the carrier have become extinct; and carriers which are extreme in the important character of length of beak originated earlier than short-beaked tumblers, which are at the opposite end of the series in this respect.
Gauza txikiak handiekin konparatuz, baldin etxe-usoaren arraza bizi eta iraungi nagusiak, beren ahaidetasunaren arabera, seriean ordenatuko balira, ordena hau ez letorke doi-doi bat haien sorrerako aldiaren ordenarekin, eta are gutxiago haien desagerpenaren ordenarekin; izan ere, haitz-uso gurasoa egun ere bizi da, eta haitz-usoaren eta mezulariaren arteko aldaki asko iraungi egin dira; eta mokoaren luzera bezalako ezaugarri inportantean ertzekoak diren mezulariak, itzulipurdikari mokomotxak baino lehenago sortu ziren, hauek ezaugarri honetan seriearen beste ertzean daudelarik.