Letter, from Antoni van Leeuwenhoek to Henry Oldenburg, dated at Delft Signed autograph Theory for the existence of different skin colours; observations of the reproduction of eels and their blood; observations of the reproduction of lice; compares the larvae of fleas with silk-worms; discusses Mr Swammerdam's views on fleas; demonstrating a grain of millet as a measure of capacity and states that he sends 8 testimonials about this (inserted after EL/L1/30); numbers of organisms living in a drop of water Testimonials from Benedict Haan, Henry Cordes, R Gordon, J Boogert, Robert Poitevin, WV Burch, Albert Hodenpijl, Alex Petrie (in Latin, Dutch and English) as witnesses to Leeuwenhoek's demonstrations Translation of letter in Latin see EL/L1/30 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 2, p 237 For summary see 'The correspondence of Henry Oldenburg', ed and trans by A Rupert Hall & Marie Boas Hall, vol 13, p 348 5 October 1677