Thanks for congratulations on Francis Darwin’s success in the tripos examinations at the university of Cambridge.

The king of Prussia has awarded him the order Pour le Mérite für Wissenschaften und Künste.

Wants to know how the colour of the eye of the peacock’s tail is produced, whether it depends upon colouring matter in the feathers or reflection, and whether any varying structural change will account for the series of colours surrounding it.

Thanks GGS for information on the peacock’s feathers. Asks whether the colour zones around the "eye" could result from varying the thickness of the film of colouring matter or whether it would require different kinds of colouring matter.