Letter, from Antoni van Leeuwenhoek to the Royal Society, dated at Delft Signed autograph Observations of the sting and the mouth parts of the gnat; observations of the mouth parts of a horse fly; concerns growing branches of vines, lime, gooseberries in normal and inverse way; investigation of germinating wheat plants; concerning soft and hard roe of cod; number of spermatozoa in a cod's soft roe Original figures no longer exist; engraved figures for publication are attached Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 7, p 343 24 August 1688