Certainly no clear line of demarcation has as yet been drawn between species and sub-species-that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at, the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences.
Dudarik ez, ez da oraindik bereiz-lerro garbirik marratu espezieen eta azpiespezieen artean, hau da, naturalista batzuen eritziz espezie mailatik oso hurbil dauden baina oraindik horretara guztiz heldu ez diren formen artean; ezta azpiespezieen eta ongi markaturiko aldakien, edo aldaki txikiagoen eta alde indibidualen artean ere.