With respect to the differences of race, a conjecture has occurred to me that much may be due to the correlation of complexion (and consequently hair) with constitution. Assume that a dusky individual best escaped miasma and you will readily see what I mean. I persuaded the Director-General of the Medical Department of the Army to send printed forms to the surgeons of all regiments in tropical countries to ascertain this point, but I daresay I shall never get any returns. Secondly, I suspect that a sort of sexual selection has been the most powerful means of changing the races of man. I can show that the different races have a widely different standard of beauty. Among savages the most powerful men will have the pick of the women, and they will generally leave the most descendants. I have collected a few notes on Man, but I do not suppose I shall ever use them. Do you intend to follow out your views, and if so would you like at some future time to have my few references and notes? I am sure I hardly know whether they are of any value, and they are at present in a state of chaos. There is much more that I should like to write but I have not strength.--Believe me, dear Wallace, yours very sincerely, CH. DARWIN. Our aristocracy is handsomer? (more hideous according to a Chinese or negro) than the middle classes, from pick of women; but oh what a scheme is primogeniture for destroying Natural Selection! I fear my letter will be barely intelligible to you. * * * * * _5 Westbourne Grove Terrace, W. May 29 [1864]._ My dear Darwin,--You are always so ready to appreciate what others do, and especially to overestimate my desultory efforts, that I cannot be surprised at your very kind and flattering remarks on my papers. I am glad, however, that you have made a few critical observations, and am only sorry you were not well enough to make more, as that enables me to say a few words in explanation.