But now let us go a step further in this imaginary case. Let us suppose that after this new creature, fish or amphibian, descended from the human race, has inhabited the water surrounding the ill-fated island for a million of years, another great change takes place. The water begins to recede from the land by gradations as slow as those by which in the former period it encroached. The land rises from the low level to which it had sunk, by volcanic action. Forests spring up upon the sides of mountains. The soil becomes firm; verdure overspreads the fields; the climate grows genial; the wilderness blossoms as the rose. Allow another million years for this restoration of the territory to an inhabitable condition. Slowly and in an unbroken series of generations the aquatic creatures, descended from the ancient human inhabitants of the island, emerge from the sea and betake themselves to the land. Modifications upon modifications accumulate, new organs are acquired; the survival of the fittest perpetuates them; the animals ascend in the scale of being, until the human type is again evolved out of the degraded descendants of the population which two millions of years previously dwelt as men upon the island, and carried on in some primitive fashion the simpler arts of human life. Is not this just as supposable as the evolution of the human race out of some lower form of organism? Are not all the elements--time, migration from one medium to another, change of conditions, and what is supposed to lead to the production of different organisms--just as powerful to produce the inferior out of the superior as to produce the superior out of the inferior, and so on interchangeably? The answer in each case is, that all such causes of modification in the animal kingdom are limited; that when once a distinct species is in existence, we have no evidence that it loses its distinct type or merges itself in another, although the earth may be full of evidence that types which formerly existed are no longer among the living organisms. FOOTNOTES: [79] "Biology," i, p. 366. [80] "In the presence of the various genealogical trees of animal descent which have been put forward so frequently of late, a judicious skepticism seems the attitude best warranted by the evidence yet obtained. If so many similar forms have arisen in mutual independence, then the affinities of the animal kingdom can never be represented by the symbol of a tree. Rather, we should conceive of the existence of a grove of trees, closely approximated, greatly differing in age and size, with their branches interlaced in a most complex entanglement. The great group of apes is composed of two such branches; but their relations one to another, to the other branches which represent mammalian groups, and to the trunks from which such branches diverge, are problems still awaiting solution."--_"Encyclopædia Britannica," article "Apes."_ [81] "Biology," i, pp. 380-382.