320 SIR JOSEPH DALTON HOOKER 



was not published till more than half a century after Hooker 

 first set foot in India. It is upon such foundations that 

 Hooker's reputation as a great constructive thinker is securely 

 based. 



The first-named of these essays will probably be estimated 

 as the most notable of them all in the History of Science. It 

 was completed in November 1859, barely a year after the joint 

 communications of Darwin and Wallace to the Linnean Society, 

 and before the Origin of Species had appeared. It was to this 

 Essay that Darwin referred when he wrote that " Hooker has 

 come round, and will publish his belief soon." But this publica- 

 tion of his belief was not merely an echo of assent to Darwin's 

 own opinions. It was a reasoned statement, advanced upon the 

 basis of his "own self-thought," and his own wide systematic and 

 geographical experience. From these sources he drew for himself 

 support for the " hypothesis that species are derivative, and mu- 

 table." He points out how the natural history of Australia seemed 

 specially suited to test such a theory,on account of the comparative 

 uniformity of the physical features being accompanied by a great 

 variety in its Flora, and the peculiarity of both its Fauna and 

 Flora, as compared with other countries. After the test had 

 been made, on the basis of study of some 8000 species, their 

 characters, their spread, and their relations to those of other 

 lands, he concludes decisively in favour of mutability and a 

 doctrine of progression. 



How highly this Essay was esteemed by his contemporaries 

 is shown by the expressions of Lyell and of Darwin. The 

 former writes: "I have just finished the reading of your splendid 

 Essay on the Origin of Species, as illustrated by your wide 

 botanical experience, and think it goes far to raise the variety- 

 making hypothesis to the rank of a theory, as accounting for the 

 manner in which new species enter the world." Darwin wrote : 

 " I have finished your Essay. To my judgment it is by far the 

 grandest and most interesting essay on subjects of the nature 

 discussed I have ever read." 



But besides its historical interest in relation to the Species 

 Question, the Essay contained what was up to its time the most 

 scientific treatment of a large area from the point of view of the 



