* * * * * _Down, Bromley, Kent, S.E. January 22, 1866._ My dear Wallace,--I thank you for your paper on Pigeons,[52] which interested me, as everything that you write does. Who would ever have dreamed that monkeys influenced the distribution of pigeons and parrots! But I have had a still higher satisfaction; for I finished yesterday your paper in the _Linnean Transactions_.[53] It is admirably done. I cannot conceive that the most firm believer in Species could read it without being staggered. Such papers will make many more converts among naturalists than long-winded books such as I shall write if I have strength. I have been particularly struck with your remarks on dimorphism; but I cannot quite understand one point (p. 22), and should be grateful for an explanation, for I want fully to understand you.[54] How can one female form be selected and the intermediate forms die out, without also the other extreme form also dying out from not having the advantages of the first selected form? for, as I understand, both female forms occur on the same island. I quite agree with your distinction between dimorphic forms and varieties; but I doubt whether your criterion of dimorphic forms not producing intermediate offspring will suffice; for I know of a good many varieties, which must be so called, that will not blend or intermix, but produce offspring quite like either parent. I have been particularly struck with your remarks on geological distribution in Celebes. It is impossible that anything could be better put, and [it] would give a cold shudder to the immutable naturalists. And now I am going to ask a question which you will not like. How does your Journal get on? It will be a shame if you do not popularise your researches. My health is so far improved that I am able to work one or two hours a day.--Believe me, dear Wallace, yours very sincerely, CH. DARWIN. * * * * * _9 St. Mark's Crescent, Regent's Park, N.W. February 4, 1866._