It is the same principle which, as I believe, accounts for the common species in each country, as shown in the second chapter, presenting on an average a greater number of well-marked varieties than do the rarer species.
Hau, nik uste, espezie arruntak herrialde bakoitzean, bigarren kapituluan agertu dudan moduan, espezie bakanagoak baino batez beste aldaki ongi markatu gehiago agertzea esplikatzen duen hastapen bera da.