I fully expect to delight in your Travels. Keep to simple style, as in your excellent letters,--but I beg pardon, I am again advising. What a capital paper yours will be on mimetic resemblances! You will make quite a new subject of it. I had thought of such cases as a difficulty; and once, when corresponding with Dr. Collingwood, I thought of your explanation; but I drove it from my mind, for I felt that I had not knowledge to judge one way or the other. Dr C., I think, states that the mimetic forms inhabit the same country, but I did not know whether to believe him. What wonderful cases yours seem to be! Could you not give a few woodcuts in your Travels to illustrate this? I am tired with a hard day's work, so no more, except to give my sincere thanks and hearty wishes for the success of your Travels. LETTER 135. TO J.D. HOOKER. Down, March 18th [1862]. Your letter discusses lots of interesting subjects, and I am very glad you have sent for your letter to Bates. (135/1. Published in Mr. Clodd's memoir of Bates in the "Naturalist on the Amazons," 1892, page l.) What do you mean by "individual plants"? (135/2. In a letter to Mr. Darwin dated March 17th, 1862, Sir J.D. Hooker had discussed a supposed difference between animals and plants, "inasmuch as the individual animal is certainly changed materially by external conditions, the latter (I think) never, except in such a coarse way as stunting or enlarging--e.g. no increase of cold on the spot, or change of individual plant from hot to cold, will induce said individual plant to get more woolly covering; but I suppose a series of cold seasons would bring about such a change in an individual quadruped, just as rowing will harden hands, etc.") I fancied a bud lived only a year, and you could hardly expect any change in that time; but if you call a tree or plant an individual, you have sporting buds. Perhaps you mean that the whole tree does not change. Tulips, in "breaking," change. Fruit seems certainly affected by the stock. I think I have (135/3. See note, Letter 16.) got cases of slight change in alpine plants transplanted. All these subjects have rather gone out of my head owing to orchids, but I shall soon have to enter on them in earnest when I come again to my volume on variation under domestication. ...In the lifetime of an animal you would, I think, find it very difficult to show effects of external condition on animals more than shade and light, good and bad soil, produce on a plant.