"How inscrutable and incomprehensible are the hidden works of Nature!" — Antonie van Leeuwenhoek

I've never taught one, because if I taught one, I'd have to teach others... I would give myself over to a slavery, whereas I want to stay a free man.

In rain water, I observed a small red worm and two other kinds of very minute insects; of those of the larger size, I judged that 30,000 together would not equal a coarse sand.

My determination is not to remain stubbornly with my ideas, but I'll leave them and go over to others as soon as I am shown plausible reasons which I can grasp.

I now found that the spider cannot fix its thread to anything without imprinting the hind part of its body on the place, by which pressure it emits an incredible number of excessively small threads diverging in every direction from whence we may conclude that as soon as the threads are exposed to the air, they lose their viscosity or gluey quality.