I have divers times examined the same matter (human semen) from a healthy man... not from a sick man... nor spoiled by keeping... for a long time and….

Man has always to be busy with his thoughts if anything is to be accomplished..

I've spent more time than many will believe [making microscopic observations], but I've done them with joy, and I've taken no notice those who have s….

Whenever I found something remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people be informed thereof..

I observed certain animalcules, within whole bodies I saw so quick a motion as to exceed belief; they were about the size of a large grain of sand, a….

I have divers times endeavoured to see and to know, what parts the Blood consists of; and at length I have observ'd, taking some Blood out of my own ….

Passing just lately over this lake, ... and examining this water next day, I found floating therein divers earthy particles, and some green streaks, ….

In the year 1657 I discovered very small living creatures in rain water..

The 4th sort of creatures... which moved through the 3 former sorts, were incredibly small, and so small in my eye that I judged, that if 100 of them….

The 31th of May, I perceived in the same water more of those Animals, as also some that were somewhat bigger. And I imagine, that [ten hundred thousa….

[M]y work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, whic….

Examining this water...I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise...and I judge that some ….