xxvi HISTORICAL SKETCH. 



long intervals by a distinct act of creative power; and 

 it is well to recollect that such an assumption is as 

 unsupported by tradition or revelation as it is opposed 

 to the general analogy of nature. If^ on the other 

 hand, we view ' Persistent Types ' in relation to that 

 hypothesis which supposes the species living at any 

 time to be the result of the gradual modification of 

 pre-existing species a hypothesis which, though un- 

 proven, and sadly damaged by some of its supporters, 

 is yet the only one to which physiology lends any 

 countenance; their existence would seem to show that 

 the amount of modification which living beings have 

 undergone during geological time is but very small in 

 relation to the whole series of changes which they have 

 suffered." 



In December, 1859, Dr. Hooker published his ' Intro- 

 duction to the Australian Flora.' In the first part of 

 this great work he admits the truth of the descent and 

 modification of species, and supports this doctrine by 

 many original observations. 



The first edition of this work was published on No- 

 vember 24th, 1859, and the second edition on January 

 7th, 1860. 



