xxv] DARWIN 21 



the facts, which involve, as Sir Joseph Hooker remarks, " a 

 continuous current of vegetation from north to south," going 

 much further back than the glacial period, because it has led 

 to the transmission not of existing species only, but of distinct 

 representative species, and even distinct genera, showing that 

 the process must have been going on long before the cold 

 period. The reason why Darwin was unaffected by these 

 various difficulties may perhaps be found in the circumstance 

 that he had held his views for so many years almost un 

 challenged. In a letter to Sir Charles Lyell, in 1866, he 

 says, "I feel a strong conviction that soon every one will 

 believe that the whole world was cooler during the glacial 

 period. Remember Hooker's wonderful case recently dis- 

 covered of the identity of so many temperate plants on the 

 summit of Fernando Po, and on the mountains of Abyssinia. 

 I look at it as certain that these plants crossed the whole of 

 Africa, from east to west, during the^same period. I wish I 

 had published a long chapter, written in full, and almost ready 

 for the press, on this subject which I wrote ten years ago. 

 It was impossible in the ' Origin ' to give a fair abstract " 

 (" More Letters," vol. i. p. 476). Having thus held his views 

 for twenty-five years, they had become so firmly impressed 

 upon his mind that he was unable at once to give them up, 

 however strong might be the arguments against them. This 

 particular difference, however, is not one which in any way 

 affects the theory of natural selection. 



4. Pangenesis, and tJie Hei-edity of Acquired Cfiaracters. 

 — Darwin always believed in the inheritance of acquired 

 characters, such as the effects of use and disuse of organs and 

 of climate, food, etc., on the individual, as did almost every 

 naturalist, and his theory of pangenesis was invented to 

 •explain this among other affects of heredity. I therefore 

 accepted pangenesis at first, because I have always felt it 

 - a relief (as did Darwin) to have some hypothesis, however 

 provisional and improbable, that would serve to explain the 

 facts ; and I told him that " I shall never be able to give it 

 up till a better one supplies its place." I never imagined 



