Letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft Signed autograph Observations of the compound eye of a beetle and calculations about the number of facets; observations through the human cornea; observations of the legs, cornea and ommatidia of a drone fly; observations of the brain of a gnat Read to the Royal Society on 11 May 1698 5 figures in red chalk attached Transcribed in JBO/10/67 See EL/L3/6 for translated extract. Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 12, p 217 Translated extract printed in Philosophical Transactions', vol 20, no 240, p 169 9 May 1698