Page - 527 - in The Origin of Species

RECAPITULATION AND CONCLUSION 527 mation will be recognised as having depended on an unusual concurrence of favourable circumstances, and the blank in- tervals between the successive stages as having been of vast duration. But we shall be able to gauge with some security the duration of these intervals by a comparison of the pre- ceding and succeeding organic forms. We must be cautious in attempting to correlate as strictly contemporaneous two formations, which do not include many identical species, by the general succession of the forms of life. As species are produced and exterminated by slowly acting and still exist- ing causes, and not by miraculous acts of creation; and as the most important of all causes of organic change is one which is almost independent of altered and perhaps sud- denly altered physical conditions, namely, the mutual rela- tion of organism to organism,—the improvement of one organism entailing the improvement or the extermination of others ; it follows, that the amount of organic change in the fossils of consecutive formations probably serves as a fair measure of the relative, though not actual lapse of time. A number of species, however, keeping in a body might remain for a long period unchanged, whilst within the same period, several of these' species by migrating into new countries and coming into competition with foreign associates, might become modified; so that we must not overrate the accuracy of organic change as a measure of time. In the future I see open fields for far more important re- searches. Psychology will be securely based on the founda- tion already well laid by Mr. Herbert Spencer, that of the necessary acquirement of each mental power and capacity by gradation. Much 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 cre- ated. To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the pro- duction 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