Determined to make GRW a geologist. Sends copy of C. Lyell [?Elements of geology (1838)].

Sends John Blackwall’s book [Researches in zoology (1834)]. Discusses his reasons for doubting that there are any marsupials in Java or Sumatra.

Thanks GRW for collection [of insects] he has made up for CD’s nephew.

Leaves decision to GRW as to which institutions should receive CD’s Beagle insects.

Testimonial letter for GRW for position at British Museum.

Classification consists of grouping beings according to descent from common stocks. Analogies are resemblances between forms not inherited from common stocks. Neither number of species nor grade of organisation should be considered in classification. Admits that caution is necessary in admitting a few species to form a group of rank equal to one containing many species.

Has no objection to uniting Monotremata and other marsupials but would object to doing so solely on ground that Monotremata consists of only two species. Members of a natural group need not share common character so long as they are linked with those which do. Believes that if every organism that ever lived were collected, a perfect series would be presented. What are reasons that unite Aptera and Diptera?

Discusses classification of animals. Degree of affinity different for different taxonomic groups. Discusses affinity of Ornithorhynchus or Echidna to reptiles.

Brain of whale is highly developed; on differences among brains of Quadrumana.

Explains what he means when he attempts a "natural classification", defining his words and using man as a standard; gives examples. Classification of Aptera and Diptera.

Discusses his discharge from the Zoological Society. Is to see Robert Brown about the British Museum position.

Congratulates GRW on appointment to position at British Museum.

Comments on GRW’s paper [Rep. BAAS (1843): 65–7; Ann. & Mag. Nat. Hist. 12 (1843): 399–412]. CD says by "link" between any two groups he never understood a half-way link, merely one in a long series. Observes that one cannot have a simple species intermediate between two great families. Criticises GRW’s use of circles to represent groups, which leads to thinking that groups are of equal value.

Regularly attends Owen’s lectures. Owen at pains to show groups are not linked. Thus makes Lepidosiren appear fish-like.

GRW thinks embryology will become chief guide to insect classification. But contradictions between classification based on embryological and adult characters do occur.

Defines the term "typical species" and discusses its use among zoologists. Cites example of type of Carnivora. Comments on general law of development of parts in animals. Cites teeth of Carnivora.

Is puzzled by CD’s question about the Viverridae; thinks if there were only one species he might regard it as an aberrant of some other group and not select it as a type of the Carnivora.

Invites GRW and his family to visit.

Discusses insects collected by CD on St Paul’s Island and the Galapagos.

Thanks him for describing the niata ox.

He is delighted that GRW is grappling with Galápagos insects. Needs to know immediately whether any entomologists beside GRW, Walker and A. White have described his insects.

Notes on Galapagos Coleoptera.

Is about to send his paper on Galapagos beetles to press. Has written some introductory material on which he invites CD’s comments.

Discusses his paper on CD’s Galapagos beetles ["Coleopterous insects … in the Galapagos Islands", Ann. & Mag. Nat. Hist. 16 (1845): 19–41] which he will forward when printed. Has drawn up descriptions of several other insects from CD’s collections.

Notes the islands, where known, on which CD’s Galapagos beetles were found. Remarks that in none of the species whose place of origin is known, does he have specimens from more than one island.