Origin of Species Variorum

forms or geographical races, crossing cannot come into play. It should also be borne in mind that the offspring from a cross between a modified and unmodified species tends partially to inherit the characters of both parents, and natural selection assuredly will preserve even slight approaches to any change of structure which is beneficial. Moreover such crossed offspring, from partaking of the same constitution with the modified parent, and from being still exposed to the same conditions, will be far more liable than other individuals of the same species again to vary or be modified in a similar manner. It has been argued that, as none of the animals and plants of Egypt, of which we know anything, have changed during the last 3000 years, so probably none have been modified in any other part of the world. The many animals which have remained unchanged since the commencement of the glacial period would have been an incomparably stronger case, for these have been exposed to great changes of climate and have migrated over great distances; whereas, in Egypt, during the last 3000 years, the conditions of life, as far as we know, have remained absolutely uniform. The fact of little or no modification having been effected since the glacial period would be of some avail against those who believe in the existence of an innate and necessary law of development, but is powerless against the doctrine of natural selection, which implies only that variations occasionally occur in single species, and that these when favourable are preserved; but this will occur only at long intervals of time after changes in the conditions of each country. As Mr. Fawcett has well asked, what would be thought of a man who argued that, because he could show that Mont Blanc and the other Alpine peaks had exactly the same height 3000 years ago as at present, consequently that these mountains