492 THE MAKING OF THE * ORIGIN ' 



Really I do not know how to thank you half for all you 

 have done for and sent to me. I might with truth do so for 

 every single paragraph in your letter and every one volume. 

 . . . Your remarks are exactly the thing, which ever since 

 being in Tierra del Fuego, I have felt a keen curiosity about, 

 and have often complained to Henslow how rarely I could 

 find any such general remarks in Botanical works. 



And in 1845 the prospective break in their personal inter- 

 course, if Hooker were elected to the chair at Edinburgh, 



is a heavy disappointment to me ; and in a mere selfish point 

 of view, as aiding me in my work, your loss is indeed irrepar- 

 able. ... I assure you deliberately that I consider all the 

 assistance which you have given me is more than I have 

 received from anyone else, and is beyond valuing in my 



More than this : they can express themselves with anima- 

 tion to each other, without risk of being misunderstood. 



Hooker contributes much from his own knowledge. Dis- 

 tribution is his favourite subject, and he supplies statistics 

 in the form desired to show range and migration, struggle 

 and survival, from the Floras of the Southern Hemisphere or 

 India or the Polar regions, all of which have fallen within his 

 direct research. Moreover, he is particularly able to tell 

 much about variation, for, as the preceding chapters show, 

 he had long been struck by the incertitude of botanists 

 on this head, and comparing detailed results all over the 

 vast fields he had covered, had found many species as de- 

 fined by local observers to be but varieties of a common 

 species with every intermediate gradation. He can put 

 Darwin in the way of answering the question whether large 

 genera with wide ranging species, as should be the case with 

 strong and increasing kinds, produce more varieties than 

 smaller groups. At the same time he adds a warning as to 

 the different impression of distinctness made on botanists by 

 a given degree of difference occurring within the large or small 

 group, so that what here would be ranked as a variety, would 

 there be ranked as a species, to the confusion of any statistics 



