Sends rock specimen for W. H. Miller. Asks JSH to see whether there is any geology in P. B. Webb and Sabin Berthelot, Histoire naturelle des Îles Canaries [1835–50]. Finds his work on geology growing so large that it will take more than one volume and asks whether this will make publication aid more difficult.

Has accepted Secretaryship of the Geological Society.

Will not come to Cambridge because "as long as I continue well I cannot bear to leave my work for half a day".

Says Colburn will allow German publisher to use copperplate and woodcuts [for Journal of researches]. Has been delayed in corrections owing to death of a relative [Josiah Wedgwood II].

Grateful for AH’s long letter and suggestions. Delighted at what he says about "complemental males". CD feared no one would believe in them but now that Owen, Dana, and AH accept them, he is content.

Agrees with AH on cross-impregnation; has collected facts on this head but has done nothing with them.

AH’s paper on Alcippe [Ann. & Mag. Nat. Hist. 2d ser. 4 (1849): 305–14] caused him to lose sleep over its anomalous structure.

Regrets ill health will prevent his attending the BAAS meeting at Edinburgh.

Refers correspondent to Descent for some information on marriage arrangements, and on the mental and moral nature of monkeys.