HISTORICAL SKETCH. XXI 



tiera, that forms now perfectly distinct have descended from a 

 single parent-form. 



In June, 1859, Professor Huxley gave a lecture before the Royal 

 Institution on the ' Persistent Types of Animal L : fe.' 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 organisation, 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 sup- 

 porters, is yet the only one to which physiology lends any counte- 

 nance ; 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 ' Introduction 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 November 24th, 

 1859, and the second edition on January 7th, 1860. v 



AJO AT 





