CD has questions related to colour differences in the sexes of butterflies, especially in relation to HWB’s paper ["On variation in sexes of Argynnis diana", Proc. Entomol. Soc. Philadelphia 4 (1865): 204–7].

Mentions that his MS on Lepidoptera [for Descent] is longer than he intended and the information is four-fifths owed to HWB.

Admires ARW’s "Theory of birds’ nests" [J. Travel & Nat. Hist. 1 (1868): 73].

Discusses their respective views on birds’ nests, sexual selection, and protection.

Asks why, if brilliant colours of female butterflies are result of protective mimicry, do not males become equally brilliant? CD believes variation in females alone accounts for it, rather than protection.

Gives details of the subjects on whom Langstaff made his observations on crying. Langstaff has not seen the platysma contract under chloroform.

Submits lists of insects [missing] for correspondent to check whether brightly coloured. Wants to determine whether there is any relation between bright colouring, whether in both sexes or one alone, and an unequal number of males and females.

Is graphically charting the sun and planets to compare them. Explains the lines and positions of bodies in his diagrams.