But as the variability of the extraordinarily-developed part or organ has been so great and long-continued within a period not excessively remote, we might, as a general rule, expect still to find more variability in such parts than in other parts of the organisation, which have remained for a much longer period nearly constant.
It would be almost superfluous to adduce evidence in support of the above statement, that specific characters are more variable than generic; but I have repeatedly noticed in works on natural history, that when an author has remarked with surprise that some important organ or part, which is generally very constant throughout large groups of species, has differed considerably in closely-allied species, that it has, also, been variable in the individuals of some of the species.
On the other hand, the points in which species differ from other species of the same genus, are called specific characters; and as these specific characters have varied and come to differ within the period of the branching off of the species from a common progenitor, it is probable that they should still often be in some degree variable,--at least more variable than those parts of the organisation which have for a very long period remained constant.
The cause of the original variability of secondary sexual characters is not manifest; but we can see why these characters should not have been rendered as constant and uniform as other parts of the organisation; for secondary sexual characters have been accumulated by sexual selection, which is less rigid in its action than ordinary selection, as it does not entail death, but only gives fewer offspring to the less favoured males.
Because in such a wilderness of running rigging, whose various different relations aloft cannot always be infallibly discerned by what is seen of them at the deck; and when the deck-ends of these ropes are being every few minutes cast down from the fastenings, it would be but a natural fatality, if, unprovided with a constant
watchman, the hoisted sailor should by some carelessness of the crew be cast adrift and fall all swooping to the sea.
The Reader will probably understand from these two instances how -- after a very long training supplemented by constant
experience -- it is possible for the well-educated classes among us to discriminate with fair accuracy between the middle and lowest orders, by the sense of sight.
The doors were in constant
banging, the stairs were never at rest, nothing was done without a clatter, nobody sat still, and nobody could command attention when they spoke.