Origin of Species Variorum

are collected from many places; and in the case of fossil species this can rarely be effected by palæontologists. We shall, perhaps, best perceive the improbability of our being enabled to connect species by numerous fine, intermediate fossil links, by asking ... ourselves whether, for instance, geologists at some future period will be able to prove that our different breeds of cattle, sheep, horses, and dogs are descended from a single stock or from several aboriginal stocks; or, again, whether certain sea-shells inhabiting the shores of North America, which are ranked by some conchologists as distinct species from their European representatives, and by other conchologists as only varieties, are really varieties, or are, as it is called, specifically distinct. This could be effected only by the future geologist discovering in a fossil state numerous intermediate gradations; and such success is improbable in the highest degree.

It has been asserted over and over again, by writers who believe in the immutability of species, that geology .. yields no linking forms. This assertion is entirely erroneous. As Sir J. Lubbock has .. remarked, "Every species is a link between other allied forms." We clearly see this if we take a genus having a score of recent and extinct species and destroy four-fifths of them; for in this case no one .. doubts that the remainder will stand much more distinct from each other. If the extreme forms in the genus happen to have been thus destroyed, the genus itself in most cases will stand more distinct from other allied genera. The camel and the pig, or the horse and the tapir, are now obviously very distinct forms; but if we add the several fossil quadrupeds which have already been discovered to the families including the camel and pig, these forms become joined by links not extremely wide apart. The