Charles Darwin on the “vain search for the undiscovered and undiscoverable essence of the term species”

“Hereafter we shall be compelled to acknowledge that the only distinction between species and well-marked varieties is, that the latter are known, or believed, to be connected at the present day by intermediate gradations, whereas species were formerly thus connected. Hence, without rejecting the consideration of the present existence of intermediate gradations between any two [...] http://bit.ly/caRFIk