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Show 422 CONCLUSION. [CHAP. XIV. with its embedded remains must not be looked at as a well-filled museum, but as a poor collection made at hazard and at rare intervals. The accumulation of each great fossiliferous formation will be recognised as havinO' depended on an unusual concurrence of circumstance~ · and the blank inte~vals between the successive stages a~ having been of vast duration. But we shall be able to guage with some security the duration of these intervals by a comparison of the preceding and succeeding organic forms.- We must be cautious in attempting to correlate as strictly contemporaneous two formations which include few ident~cal species, b_y the general sucdession of their forms of hfe. As species are produced and exterminated b~ slowly acting and s.till existing causes, and not by miraculo~s acts of creation and by catastrophes; and as the most Important of all causes of organic change is one which is aln1ost in~ependen.t .of altered and perhaps sudder; ly altered P.hyswal conditions, namely, the mutual rela~ Ion of o::~an1sm t? organism,-the improvement of one bmng entailing the Improvement or the extermination of others ; . it follows, tha.t the amount of organic change in th.e fossils of consecutive formations probably serves as a fair .measure of the lapse of actual time. A number of species, ~owever, keeping in. a b~d:J: mig~t remain for a long period unchan~ed, whil~t WI~hin. this same period, several o~ the~e spemes, bY: l!ngrating Into new countries and coming Into competition with foreign associates ~ight become modified ; so that we must not overrate th~ accuracy of organic change as a measure of time. Durin~ e.arly periods of the earth's history, when the forms of life were probably fewer and simpler, the rate of change was probably slower; and at the :first dawn of life when very few forms of the simplest structure existed the rate of change may have been slow in an extrem~ degree. The whole history of the world, as at present known, althou~? of a lengt~ quite incomprehensible by us, will hereafte~ be recognised a~ a mere fragment of time, compared With the ages which have elapsed since the :first creature, the progenitor of innumerable extinct and living descendants, was created. CHAP. XIV.] CONCLUSION. 423 In the distant future I see open :fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history. Authors of the highest eminence seem to be fully satisfied with the view that each species has been independently created. To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual. When I view all beings not as special creations, but as the lineal descendants of some few beings which lived long before the :first bed of the Silurian system was deposited, they seem to me to become ennobled. Judging from the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity. And of the species now living very few will transmit progeny of any kind to a far distant futurity; for the manner in which all organic beings are grouped, shows that the greater number of species of each genus, and all the species of n1any genera, have left no descendants, but have become utterly extinct. We can so far take a prophetic glance into futurity as to foretel that it will be the common and widely-spread species, belonging to the larger and dominant groups, which will ultimately prevail and procreate new and dominant species. As all the living forms of life are the lineal descendants of those which lived long before the Silurian epoch, we may feel certain that the ordinary succession by generation has never once been "Qroken, and that no cataclysm has desolated the whole world. Hence we may look with some confidence to a secure futnre of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection. It is interesting to contemplate an entangled bank, . clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and |
