The Complete Work of Charles Darwin Online

RECORD: Darwin, C. R. 1861.10.17. [Note on Gradation]. CUL-DAR48.A48. Edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)

REVISION HISTORY: Transcribed by Christine Chua and edited by John van Wyhe 9.2021. RN1

NOTE: See record in the Darwin Online manuscript catalogue, enter its Identifier here. Reproduced with permission of the Syndics of Cambridge University Library and William Huxley Darwin. The volume CUL-DAR48 contains notes for Natural selection chap. 8 'Transitions of Organs'. Notes on bees' cells for origin of species theory.

[A48]

Oct 17/61 Gradation Ch 8

To take an example from mollusca.

Clavigella, one of most wonderful molluscs G. B. Sowerby says one valve produced into gut tube. Aspergillum both valves produced - Teredo - has fleshy tube and lines its passage with calc. matter but neither valve produced - But is Teredo allied to above - G.B.S. says that Pholas - sometimes has one valve produced - All this gradation could be illustrated by woodcuts.

If true gradation might be shown from Bivalves. to Univalves - Mr. G.B.S. says some Secondary fossils seem to fill up group.

Citation: John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)