xiv HISTORICAL SKETCH. 



In June, 1859, Professor Huxley gave a lecture before 

 the Boyal Institution on the "Persistent Types of Animal 

 Life." Referring to such cases, he remarks, " It is difficult 

 to comprehend the meaning of such facts as these, if we 

 suppose that each species of animal and plant, or each 

 great type of organization, was formed and placed upon the 

 surface of the globe at 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 unproven, 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 modificav 

 tion 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 "Introduc- 

 tion 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 observa- 

 tions. 



The first edition of this work was published on November 

 4, 1859, and the second edition on January 7, 1860. 



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