Practically, when naturalists are at work, they do not trouble themselves about the physiological value of the characters which they use in defining a group or in allocating any particular species.
Praktikan, naturalistek lanean dihardutenean, ez dute izaten kezkarik talde bat definitzeko edo espezie jakin bat kokatzeko erabiltzen dituzten ezaugarrien balio fisiologikoaz.