308 ORDER AND SUCCESSION OP LIFE. 



Such seems to have been and to be the destined order 

 and succession of vitality. As in existing plants and ani- 

 mals we perceive a vast variety of grades from lower to 

 higher forms, so throughout the development of Life in 

 time there has been a coincident ascent from the lower 

 to the higher ,orders. During the primary periods the 

 lands and waters were peopled only by the lowest forms ; 

 but as time rolled on, higher and higher orders gradually 

 made their appearance, each successive rock-system bearing 

 testimony to the introduction of newer and more highly 

 organised existences. Imperfect as the geological record 

 admittedly is, and limited as may be the portions of the 

 earth's crust yet examined, there is such a coincidence in 

 the fossil life of all the surveyed tracts, that we may 

 regard the order of ascent as an established fact, subject 

 only to minor modifications in the details. The differences 

 that have arisen ainong geologists relate not to the facts of 

 the ascent, but to the mode or modes in which the de- 

 velopment has been brought about. As we know more of 

 extinct life and more of the physiology of existing life, 

 these differences will in a great measure disappear, and 

 conflicting hypotheses give way to a uniform and satisfac- 

 tory theory. In the mean time every earnest endeavour 

 is entitled to our regard, and however startling its views, 

 or how little soever it may seem to clear the way to sounder 

 conclusions, it ought to be gratefully received as a contribu- 

 tion towards the solution of the highest and most interest- 

 ing problems, perhaps, that the progress of discovery has 

 submitted to the consideration of modern philosophy. 



character, especially if it should be in the ascensive direction, there 

 might be associated powers of penetrating the problems of zoology, so 

 far transcending those of our present condition as to be equivalent to a 

 different and higher phase of intellectual action, resulting in what might 

 be termed another species of zoological science." Preface to Comparative 

 Anatomy and Physiology of Vertebrates. 



