Darwin states he hopes ARW's paper on sexual modifications and adaptive mimicry in butterflies will be published.

Susan Darwin still lives, but is dying.

Requests an Erica massoni to compare with Drosera.

On L. Agassiz’s "astonishing" view that Amazon Valley was filled with gigantic glacier. Asa Gray says LA is determined to cover the globe with glaciers in order to destroy "Darwinian views".

Excellent review of A. Murray [The geographical distribution of mammals] in Gardeners’ Chronicle [(1866): 902].

Frankland’s Royal Institution lecture ["On the source of muscular power" Not. Proc. R. Inst. G. B. 4 (1862–6): 661–85].

Wallace’s paper.