Origin of Species Variorum

Comparison with 1872

fossils in the formations above and below, is simply explained by their intermediate position in the chain of descent. The grand fact that all extinct .. beings can be classed with all recent beings, naturally follows from the living and the extinct being the offspring of common parents. As species have generally diverged in character during their long course of descent and modification, we can understand why it is that the more ancient forms, or early progenitors of each group, so often occupy a position in some degree intermediate between existing .. groups. Recent forms are generally looked upon as being, on the whole, higher in the scale of organisation than ancient .. forms; and they must be higher, in so far as the later and more improved forms have conquered the older and less improved forms in the struggle for life; they have also generally had their organs more specialised for different functions. This fact is perfectly compatible with numerous beings still retaining a simple and little improved organisation fitted for simple conditions of life; it is likewise compatible with some forms having retrograded in organisation, though becoming under each grade of descent better fitted for their changed and degraded habits of life. Lastly, the wonderful law of the long endurance of allied forms on the same continent,— of marsupials in Australia, of edentata in America, and other such cases,— is intelligible, for within the same country the existing and the extinct will .. be closely allied by descent.

Looking to geographical distribution, if we admit that there has been during the long course of ages much migration from one part of the world to another, owing to former climatal and geographical changes and to the many occasional and unknown means of dispersal, then we can understand, on the theory of descent with modification, most of the great leading facts in Distribution. We can see why there should be so striking a parallelism in the distribution of organic beings throughout space, and in their geological succession throughout time; for in both cases the beings have been connected by the bond of ordinary generation, and the means of

fossils in the formations above and below, is simply explained by their intermediate position in the chain of descent. The grand fact that all extinct organic beings belong to the same system with recent beings, falling either into the same or into intermediate groups, follows from the living and the extinct being the offspring of common parents. As the groups which have descended from an ancient progenitor have generally diverged in character, the progenitor with its early descendants will often be intermediate in character in comparison with its later descendants; and thus we can see why the more ancient a fossil is, the oftener it stands in some degree intermediate between existing and allied groups. Recent forms are generally looked at as being, in some vague sense, higher than ancient and extinct forms; and they are in so far higher as the later and more improved forms have conquered the older and less improved organic beings in the struggle for life. ↑ Lastly, the law of the long endurance of allied forms on the same continent,— of marsupials in Australia, of edentata in America, and other such cases,— is intelligible, for within a confined country, the recent and the extinct will naturally be allied by descent.