Just finished HWB’s paper ["Contributions to an insect fauna of the Amazon valley", Trans. Linn. Soc. Lond. 23 (1862): 495–566], one of the most remarkable he has ever read. Found mimetic cases and connection of facts marvellous. Finds equally important the facts on variation and segregation of complete and semi-complete species. Questions whether insect mimicry is not due to small size and defencelessness. Criticises title of paper. Mentions that Wallace will appreciate it.

Gratified by CD’s approval of paper which was also praised by Hooker and Wallace. Only cares for one other opinion, that of C. Felder of Vienna. He finds ordinary entomologists are not scientific men. Asks for more criticisms; desires to publish paper in a widely circulating journal to advertise his book.

[Apparently in reply to question in missing portion of 3825.] A written agreement is unnecessary, but a letter stating terms would prevent misundertanding. He will attempt to have a review of HWB’s paper published.