No book has made such a powerful impression on EH as the Origin. Most older German scholars opposed to it, but number of supporters growing among the young. Fortunately strength of religious dogmas now small among educated Germans. Situation in Jena especially favourable. Defended CD’s theory last year at Congress of German Scientists in Stettin.

Intends special study of jellyfish.

Plans general work on natural history.

Hard fate [death of Anna Sethe Haeckel] has made EH indifferent to criticism.

Colleagues August Schleicher and Carl Gegenbaur also convinced by CD’s theory.

Thanks for praise [of Origin].

Comments on EH’s Die Radiolarien.

Grieved EH has suffered calamity [death of Anna Sethe Haeckel].

CD recovering from long illness.

Doing easy botanical work.

Mentions variability.

Discusses reception of CD’s views in Germany.

Sends photographs of himself and his late wife [Anna Sethe]. Describes death of his wife.

Plans trip to the Alps.

Thanks CD for biographical information about himself.

Mentions Goethe as early evolutionist.

Cites Kant as early supporter of epigenesis.

Mentions criticism of CD’s theory by R. A. von Kölliker ["Über die Darwin’sche Schöpfungstheorie", Z. Wiss. Zool. 14 (1864): 174–86].

Can understand EH’s feelings on death of his wife.

CD was impressed by manner in which species in South America are replaced by closely allied ones, by affinity of species inhabiting islands near S. America, and by relation of living Edentata and Rodentia to extinct species. When he read Malthus On population, the idea of natural selection flashed on him.

Agrees with EH’s remarks on Kölliker ["Darwin’sche Schöpfungstheorie", Z. Wiss. Zool. 14 (1864): 174–86].

Asks EH to thank Carl Gegenbaur [for Vergleichende Anatomie der Wirbelthiere (1864)].

Thanks CD for notes concerning the development of his ideas about the origin of species. Says August Schleicher and Carl Gegenbaur also interested.

Names new supporters of CD’s theory, including Max Schultze, Rudolf Leuckart, and Alexander Braun. Zoologists have been more interested than botanists.

He is writing a general work on the relationships among animals [Generelle Morphologie der Organismen (1866)].

Comments on Fritz Müller’s Für Darwin [1864].

Gegenbaur is revising his Grundzüge der vergleichenden Anatomie [2d ed. (1870)] to accord with evolution.

Thanks CD for copy of book on balanids [Living Cirripedia, vol. 2].

Sends Living Cirripedia [vol. 2].

Has employed translator for Fritz Müller’s book [Für Darwin (1864)].

Thanks for paper and speech.

Has heard from Huxley that CD has been ill.

Progress on his book [Generelle Morphologie (1866)] has been slow.

Has been named "ordentlicher Professor". Has 150 listeners in his lectures on CD’s theory.

Thanks CD for copy [of "Climbing plants"].

Sends his book [Beiträge zur Naturgeschichte der Hydromedusen, 1. Heft: Die Familie der Rüsselquallen (Geryonidae) (1865)] and two articles.

Calls attention to a new rhizopod from Nice.

Not surprised at delay of his book [Generelle Morphologie (1866)].

P. M. Duncan taking side of evolution.

Has received paper on Geryonidae ["Über eine neue Form des Generationswechsels bei den Medusen", Monatsber. K. Akad. Wiss. Berlin (1865): 85–94]. Had often speculated on whether such a case ever occurred in nature.

Comments on CD’s health.

Discusses origin of life and differentiation of principal classes of plants and animals.

Discusses Generelle Morphologie and its chapter on embryological development.

His lectures on CD’s theory.

Asks CD for larger portrait of himself and for several copies of the small photograph. Will send photographs of German scientists in exchange.

Sends copies of photographs of himself. Asks for photographs of German naturalists.

Comments on EH’s account of Protogenes primordialis.

Discusses exchange of photographs with German scientists.

Comments on attitudes of German scientists toward CD’s theory.

Names several scientists who exchanged photographs: Braun, Virchow, Leydig, and Dohrn.

Thanks for photographs [of German scientists].

Comments on sheet of EH’s Generelle Morphologie [1866]. In emphasising divergence of character EH shows his clear understanding of CD’s views. It was years before CD saw necessity of divergence.

Interested in Carl Claus [Copepodenfauna von Nizza (1866)].

Explains how to get to Down for visit.

Will visit CD on Sunday, 21 October.

Will spend winter in research on Madeira and Tenerife.

CD will soon receive copy of Generelle Morphologie.

Comments on EH’s "great work" [Generelle Morphologie].

An English translation "hopeless".

Asks about EH’s expedition.

MS of Variation sent to printers.

Fritz Müller working on plants.

Struck by singular clarity of EH’s Generelle Morphologie. Remarks on various authors seem too severe. Severity leads the reader to take the side of the attacked person.

Making slow progress in correcting Variation.

Thanks CD for new edition of Origin [4th ed. (1866)].

Comments on CD’s criticism of the harsh tone of Generelle Morphologie. Thinks he may have harmed himself but not the cause. Believes a radical reform of the science necessary, and since most scientists take a prejudiced view of the matter, a vigorous attack is essential.

Describes his travels in Canaries, Spain, and France.

Discusses his previous criticisms of EH’s Generelle Morphologie. Fears it will make enemies.

Discusses reception of descent theory in England.

Mentions EH’s trip to Canary Islands.

Is engaged to marry Agnes Huschke. Will make wedding trip to Switzerland and Italy in autumn; therefore cannot visit CD as hoped.

Discusses present research. Comments on Protoamoeba with respect to origin of life. Says it makes question of common or separate origin of phyla unimportant.

CD to receive honorary diploma from Imperial Zoological Botanical Society in Vienna.

Sends photograph of Viennese botanist, August Kanitz.