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 



