Thanks LB for copy of his Aus Natur und Wissenschaft [1862]. Responds to LB’s comment [on Origin].

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.

[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.