Letter, from Antoni van Leeuwenhoek to Hans Sloane, dated at Delft Observations of spermatozoa from cod; calculation of its size; observations of spermatozoa from ram and pike Read to the Royal Society on 28 May 1701 Translated extract see EL/L3/28a Transcribed in JBO/10/219 Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 13, p 291 English translation printed in 'Philosophical Transactions', vol 22, no 270, p 821 15 April 1701