Ɛpsilon

To B. W. Savile   [before 8 October 1881]1

[Such, however, was not the case with Mr. Darwin.2 When I subsequently ventured to put the similar question to the master, he at once most kindly favoured me with the following reply, which I give in his own words, in order to avoid anything like a mis-statement of his views:— After speaking of there being “some gradation in perfection with mammals in the mammery glands,” and the custom of the young in the Echidna (of the crab family), and the Ornithoptera (of the butterfly species) “to suck off the surface of its skin, to secrete milk, for there is no nipple,” Mr. Darwin added: ‘In the case of certain fish the ova are hatched in a marsupal sack on the surface of the stomach of the male, and the young when hatched feed on the mucus secreted from the skin lining the sack; and here as I believe, we see what might be the commencement of a simple mammery gland as in Echidna, &c. This is of course only an hypothesis. The exact steps in the evolutionary process could be discovered only by the observation of animals which became extinct during the earliest part of the secondary period.”3]

incomplete

1
The date is established by the relationship between this letter and the letter from B. W. Savile, 10 October 1881, in which Savile stated that his reply was delayed because he had been away for two days.
2
These letter fragments are from an article published by Savile in the Record, an Anglican newspaper, after CD’s death. In the article, Savile reported that before writing to CD he had asked John Tyndall ‘how could the first of the mammal species be nourished, if its immediate progenitor was a non-mammal’. Tyndall did not reply.
3
Although Savile was claimed to be quoting CD’s words, he clearly had no understanding of the animals to which CD referred. The Echidna is not a genus of crabs, but an egg-laying mammal of the order Monotremata, known as a spiny anteater. Ornithoptera is a butterfly genus, but it is more likely that CD wrote Ornithorhynchus (duck-billed platypus), the only other living mammal that lays eggs. In Origin 6th ed., pp. 189–90, CD had used the example of Ornithorhynchus anatinus, which had a rudimentary breast but no nipple, to discuss the origin of mammary glands. He had also referred to the fish Hippocampus, which develops its young in a marsupial sack after their emergence from eggs (ibid., p. 189).

Please cite as “DCP-LETT-13366,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-13366