Sends papers on graft-hybrids ["Sur les hybrides obtenus par la greffe", Bull. Congr. Int. Bot. & Hortic. Amsterdam (1865): 65–80, and "Über Mischlinge, durch Pfropfen entstanden", Sitzungsber. K. Phys.-oekon. Ges. Königsberg 6 (1865): 11–21].

Lyell wants to see JDH’s last letter [the part on glacial periods]. Lyell full of concern about astronomical causes of heat and cold on the globe.

Encloses letter from John Scott.

Has received the larva of the batrachian. Outlines its affinities. Problems of batrachian systematics.

Refers to part of JDH letter on glacial period sent on to Lyell. CD will not yield. Cannot think how JDH attaches so much attention to physicists. Has "come not to care at all for general beliefs without the special facts".

His health is improved but not so good as JDH supposes.

Would much like to see Dr Birchfield appointed superintendent of the new asylum at Woking.

As Honorary Secretary of the Botanical Congress he asks that CD’s name be listed as a member of its committee.

Discusses the stinging habits of wasps and bees and whether or not they leave their sting in the wound.

Feels sure that at times the globe must have been superficially cooler. Believes CD will turn out right with regard to migration across the equator via mountain chains, while the tropical heat of certain lowlands was retained.

The specimen is not a fish but the larva of some batrachian or frog-like animal. Has sent it to British Museum, which says it resembles the axolotl of Mexico.

Has returned memorial to Chancellor of Exchequer; thanks CL for his note.

Lengthy remarks on cool period. Did not know of CL’s interest. New facts in new German and English [4th] editions of Origin will be too late for CL’s use. CD’s ten-year-old MS on cool period is available.

Thanks RC for photograph and for papers, which are of highest interest to CD. He is not fully convinced about the rose by RC’s graft-hybrid paper [Bull. Congr. Int. Bot. & Hortic. Amsterdam (1865): 65–80]. Still retains faith in his own view that no plant is perpetually self-fertilised.

Surprised at Hooker’s introducing "so organic a change as a deviation in the axis of the planet" to explain the cold of the Glacial Period.

Thanks CD for German translation of Origin.

Droughts over the summers have brought about changes in the numbers of plants and animals in the area. The small quantity of Orchestia darwinii that has survived the changes no longer includes two previously common male forms. Great changes also take place without such unusual physical conditions. The disappearance of a briefly abundant bryozoan in local caves has made way not for the return of original bryozoan inhabitants but for a completely new fauna.

Reviewing C. V. Naudin’s article ["Nouvelles recherches sur l’hybridité dans les végétaux", Ann. Sci. Nat. (Bot.) 4th ser. 19 (1863): 180–203] for Popular Science Review [5 (1866): 304–13]. Requests references.

Proposes to visit Down on Easter weekend.

Gives details of enclosed MS on cool period. Mentions Hooker’s opposed "axis of the earth" view. Causes of glacial period are beyond CD; "cannot believe change in land and water being more than a subsidiary agent".

Comments on cool-period MS. Still believes geographical changes principal cause of former changes of climate.

Thanks for references for his Naudin–hybridism paper [see 5029].

On the "bullae" as constant, regular generic characters in Hymenoptera. Disagrees with Louis Jurine ["Observations sur les ailes des hyménoptères", Mem. Accad. Sci. Torino 24 (1820): 177–214].

Asks, on behalf of his father, whether he might publish a new German translation of the Origin, believing Bronn’s to be inadequate.

Forgot to thank CD for his praise of tendril paper [see 4944].