so in space, it certainly is the general rule that the area inhabited by a single species, or by a group of species, is continuous, and the exceptions, which are not rare, may, as I have attempted to show, be accounted for by former migrations under different circumstances, or through occasional means of transport, or by the species having become extinct in the intermediate tracts.
lehenago, egoera ezberdinetan, izandako migrazioengatik, noizbehinkako garraiabideak tartean izan direlako, edo bitarteko guneetan espezieak iraungi egin direlako.