SIR JOSEPH HOOKER LANKESTER. 593 



publications, but are most fully set forth in his Introductory Essay 

 to the Flora Tasmaniae, dealing with the Antarctic flora as a whole. 

 His study of Darwin's plants from the Galapagos Islands and 

 their relation to those of other tropical islands and of the South 

 American Continent brought him into close relation with Darwin, 

 whom he visited in 1817. This was the beginning of their memor- 

 able intimacy and continuous exchange of letters (contained in these 

 volumes and the similar Life and Letters of Darwin). These letters 

 w.ere really conversations as to endless botanical details — inquiries 

 made and answered, criticisms and arguments submitted by one to 

 the other. They form a record of surpassing interest to all future 

 generations of biologists. Hooker's stores of knowledge of fact in 

 every department of botanical science were of essential service to 

 Darwin, while Darwin's marvelous fecundity in original suggestions 

 as to the explanation and the significance of facts and his remorse- 

 less criticism of those suggestions by appeal to other facts and to 

 experiment, were a perennial stimulus to Hooker, who was himself 

 a theorist, a generalizer — what is sometimes called " a philosopher " 

 — of large outlook. Lyell wrote in 1859 to Hooker of the Introduc- 

 tory Essay to the Flora Tasmaniae: 



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. 



And 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. 



Hooker was the earliest prominent naturalist to declare his ad- 

 hesion to the theory of the Origin of Species by Natural Selection 

 set forth by Darwin in his historic volume of 1859, but his complete 

 adhesion to it was only arrived at by long and minute discussion 

 with Darwin of his data, his arguments, and inferences, extending 

 over some years both before and after 1859, in which the two 

 naturalists were in constant communication. It must be borne in 

 mind that Darwin's theory of the survival of favored varieties by 

 natural selection was something additional to the hypothesis of the 

 derivative origin of species which Hooker had supported. Dar- 

 win's theory gave an explanation of that derivation, and showed it 

 to be the necessary result of existing natural causes. 



Hooker continued during the next 22 years to take a leading part 

 in the development of an understanding of the geographical distri- 

 bution of organisms on the earth's surface in the light of Darwin's 

 great doctrine of natural selection. He was at times much per- 

 plexed by the attempt to demarcate natural phyto-geographical 

 provinces and subprovinces, as distinct from merely topographical 



