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Show 46 lJARWINIANA. The limits allotted to this article are nearly reached, yet only four of the fourteen chapters of the volume have been touched. These, however, contain the fundamental principles of the theory, and most of those applications of it which are capable of something like verification, relating as they do to the phenomena now occurring. Some of our "extracts also show how these principles are thought to have operated through the long lapse of the ages. The chapters from the sixth to the ninth inclusive are designed to obviate difficultjes and objections, "some of them so grave that to tllis day," the author frankly says, he "can never reflect on them without being staggered." We do not wonder at it. After drawing what comfort he can from "the imperfection of the geological record" (Chapter IX.), which we suspect is scarcely exaggerated, the author considers the geological succession of organic beings (Chapter X.), to see whether they better accord with the common view of the immutability of species, or with that of their slow and gradual modification. Geologists must settle that question. Then follow two most interesting and able chapters on the geographical distribution of plants and animals, the summary of which we should be glad to cite; then a fitting chapter upon classification, morphology, embryology, etc., as viewed in the light of this theory, closes the argument; the fourteenth chapter being a recapitulation. The interest for the general reader heightens as the author advances ·on his perilous ·way and grapples manfully with the most formidable difficulties. To account, upon these principles, for the gradual THE ORIGIN OF SPECIES. 47 elimination and · segregation of nearly allied formssuch as varieties, sub-species, and closely-related or representative species-:also in a general way for their geographical association and present range, is comparatively easy, is apparently within the bounds of possibility. Could we stop here we shouJd be fairly contented. But, to complete the system, to carry o.ut the principles to their ultimate conclusion, and to explain by them many facts in geographical distribution which would still remain anomalous, Mr. Darwin is equally bound to account for the formation of genera, families, ·orders, and even classes, by natural selection. He does "not doubt that the theory of descent with modification embraces all the members of the same class," and he concedes that analogy would press the conclusion still further; while he admits that "the more distinct the forms are, the more the arguments fall away in force." To command assent we naturally require decreasing probability to be overbalanced by an increased weight of evidence. An opponent might plausibly, and perhaps quite fairly, urge that the links in the chain of argument are weakest just where the greatest stress falls upon them. To which Mr. Darwin's answer is, that the best parts of the testimony have been lost. He is confident that intermediate forms must have existed; that in the olden times when the genera, the families, and the orders, diverged from their parent stocks, gradations existed as fine as those wl1ich now connect closely related species with varieties. But they have passed and left no sign. The geological :r:ecord, even if all displayed to view, is a book from which not only many |
