The discussion on European Genera is profoundly interesting; but here alone I earnestly beg for more information, viz. to know which of these genera are absent in the Tropics of the world, i.e. confined to temperate regions. I excessively wish to know, ON THE NOTION OF GLACIAL MIGRATION, how much modification has taken place in Australia. I had better explain when we meet, and get you to go over and mark the list. ... The list of naturalised plants is extremely interesting, but why at the end, in the name of all that is good and bad, do you not sum up and comment on your facts? Come, I will have a sneer at you in return for the many which you will have launched at this letter. Should you have remarked on the number of plants naturalised in Australia and the United States UNDER EXTREMELY DIFFERENT CLIMATES, as showing that climate is so important, and [on] the considerable sprinkling of plants from India, North America, and South Africa, as showing that the frequent introduction of seeds is so important? With respect to "abundance of unoccupied ground in Australia," do you believe that European plants introduced by man now grow on spots in Australia which were absolutely bare? But I am an impudent dog, one must defend one's own fancy theories against such cruel men as you. I dare say this letter will appear very conceited, but one must form an opinion on what one reads with attention, and in simple truth, I cannot find words strong enough to express my admiration of your essay. My dear old friend, yours affectionately, C. DARWIN. P.S.--I differ about the "Saturday Review". ("Saturday Review", December 24, 1859. The hostile arguments of the reviewer are geological, and he deals especially with the denudation of the Weald. The reviewer remarks that, "if a million of centuries, more or less, is needed for any part of his argument, he feels no scruple in taking them to suit his purpose.") One cannot expect fairness in a reviewer, so I do not complain of all the other arguments besides the 'Geological Record' being omitted. Some of the remarks about the lapse of years are very good, and the reviewer gives me some good and well-deserved raps--confound it. I am sorry to confess the truth: but it does not at all concern the main argument. That was a nice notice in the "Gardeners' Chronicle". I hope and imagine that Lindley is almost a convert. Do not forget to tell me if Bentham gets all the more staggered. With respect to tropical plants during the Glacial period, I throw in your teeth your own facts, at the base of the Himalaya, on the possibility of the co-existence of at least forms of the tropical and temperate regions. I can give a parallel case for animals in Mexico. Oh! my dearly beloved puny child, how cruel men are to you! I am very glad you approve of the Geographical chapters... CHARLES DARWIN TO C. LYELL. Down, [January 4th, 1860]. My dear L.