190 EVOLUTION [CHAP. Ill 



Letter 129 should esteem it a great favour if you will allow me to call 

 on you and have half an hour's conversation with you. 



As far as I am personally concerned, I am sure I ought to 

 be grateful to you, for since my accident nothing has given 

 me so much pleasure as the perusal of your book. Such 

 studies are now a great resource to me. 



Letter 130 To C. Lyell. 



2, Hesketh Terrace, Torquay [Aug. 2nd, 1861]. 



I declare that you read the reviews on the Origin more 

 carefully than I do. I agree with all your remarks. The 

 point of correlation struck me as well put, and on varieties 

 growing together ; but I have already begun to put things in 

 train for information on this latter head, on which Bronn 

 also enlarges. With respect to sexuality, I have often 

 speculated on it, and have always concluded that we are too 

 ignorant to speculate : no physiologist can conjecture why the 

 two elements go to form a new being, and, more than that, 

 why nature strives at uniting the two elements from two 

 individuals. What I am now working at in my orchids is 

 an admirable illustration of the law. I should certainly 

 conclude that all sexuality had descended from one prototype. 

 Do you not underrate the degree of lowness of organisation 

 in which sexuality occurs viz., in Hydra, and still lower in 

 some of the one-celled free confervae which "conjugate," 

 which good judges (Thwaites) believe is the simplest form of 

 true sexual generation ? 1 But the whole case is a mystery. 



There is another point on which I have occasionally 

 wished to say a few words. I believe you think with Asa 

 Gray that I have not allowed enough for the stream of 

 variation having been guided by a higher power. I have 

 had lately a good deal of correspondence on this head. 

 Herschel, in his Physical Geography? has a sentence with 



1 See Letter 97. 



2 Physical Geography of the Globe, by Sir John F. W. Herschel, Edin- 

 burgh, 1861. On p. 12 Herschel writes of the revelations of Geology 

 pointing to successive submersions and reconstructions of the continents 

 and fresh races of animals and plants. He refers to a " great law of 

 change" which has not operated either by a gradually progressing variation 

 of species, nor by a sudden and total abolition of one race. . . . The 

 following footnote on page 12 of the Physical Geography was added in 



