Letter, from Antoni van Leeuwenhoek to Robert Hooke, dated at Delft Concerning the germinal spot of an egg; microscopic observations of oak, elm, beech, willow, alder, ebony, box wood, straw; discusses the movement of water in tree vessels; observations of the sperm of various fish Leeuwenhoek adds a note about his diagram of the circumference of an imaginary oak, alder etc showing annual growth rings 25 figures - five are in pencil and the others in red chalk- of transverse or tangential sections of different species of wood Transcribed and translated in 'Alle de brieven van Antoni van Leeuwenhoek', edited, illustrated and annotated by Committee of Dutch Scientists, vol 3, p 145 Printed in 'Philosophical Transactions', vol 13, no 148, p 197 12 January 1680