Thinks GHL’s articles are quite excellent; hopes they will be republished.

Discusses adaptation. Doubts whether similar conditions without selection can produce similar organs independent of blood relationship: "resemblances due to descent and adaptation can commonly be distinguished".

Discusses luminous insects, electrical organs of fish, thorns and spines.

Gratified by CD’s approval of his articles, which the public has not much liked.

Clarifies the obscure sentence CD criticised – forms having a different genesis can be similar.

Calls CD’s attention to Kovalevsky’s memoir on Amphioxus [Mem. Acad. Imp. Sci. St.-Pétersbourg 7th ser. 11 (1868) no.4]. K’s views are all in favour of CD’s and against GHL’s.