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Darwin Correspondence Project

To C. G. Semper   18 July 1877

Down, | Beckenham, Kent. | (Railway Station | Orpington. S.E.R.)

July 18th. 1877

My dear Sir

I received safely this morning your Memoir together with your kind note. The figures are wonderful, & I find that I understood rightly parts of what I saw in the slides which you sent me. What a very curious reaction between the fish & the slug! I suppose that the latter remains motionless if it sees with its dorsal eyes the fish.1

I can assure you that I feel deeply the honour of so remarkable a Memoir having been dedicated to me.

I wish you a pleasant & successful expedition to the U. States, & remain | My dear Sir | Yours faithfully & obliged | Charles Darwin


See letter from C. G. Semper, 13 July 1877. Semper had sent CD his Über Sehorgane von Typus der Wirbelthieraugen auf dem Rücken von Schnecken (On visual organs of the vertebrate eye type on the backs of slugs; Semper 1877b). Semper hypothesised that the sea slug Onchidium developed dorsal eyes in regions where it was hunted by the mud skipper, Periophthalmus.


Thanks for CGS’s work [“Über Schneckenaugen” (1877)].

Letter details

Letter no.
Charles Robert Darwin
Carl Gottfried Semper
Sent from
Source of text
Universitäts- und Landesbibliothek Düsseldorf (slg 60/Dok/56)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 11061,” accessed on 5 August 2021,