C.D.--Memory very bad for dates, and for learning by rote; but good in retaining a general or vague recollection of many facts. R.D.--Wonderful memory for dates. In old age he told a person, reading aloud to him a book only read in youth, the passages which were coming--knew the birthdays and death, etc., of all friends and acquaintances. STUDIOUSNESS? C.D.--Very studious, but not large acquirements. R.D.--Not very studious or mentally receptive, except for facts in conversation--great collector of anecdotes. INDEPENDENCE OF JUDGMENT? C.D.--I think fairly independent; but I can give no instances. I gave up common religious belief almost independently from my own reflections. R.D.--Free thinker in religious matters. Liberal, with rather a tendency to Toryism. ORIGINALITY OR ECCENTRICITY? C.D.-- -- Thinks this applies to me; I do not think so--i.e., as far as eccentricity. I suppose that I have shown originality in science, as I have made discoveries with regard to common objects. R.D.--Original character, had great personal influence and power of producing fear of himself in others. He kept his accounts with great care in a peculiar way, in a number of separate little books, without any general ledger. SPECIAL TALENTS? C.D.--None, except for business as evinced by keeping accounts, replies to correspondence, and investing money very well. Very methodical in all my habits. R.D.--Practical business--made a large fortune and incurred no losses. STRONGLY MARKED MENTAL PECULIARITIES, BEARING ON SCIENTIFIC SUCCESS, AND NOT SPECIFIED ABOVE? C.D.--Steadiness--great curiosity about facts and their meaning. Some love of the new and marvellous. R.D.--Strong social affection and great sympathy in the pleasures of others. Sceptical as to new things. Curious as to facts. Great foresight. Not much public spirit--great generosity in giving money and assistance. N.B.--I find it quite impossible to estimate my character by your degrees. The following letter refers inter alia to a letter which appeared in 'Nature' (September 25, 1873), "On the Males and Complemental Males of certain Cirripedes, and on Rudimentary Organs:"] CHARLES DARWIN TO E. HAECKEL. Down, September 25, 1873. My dear Haeckel,