black
grey
blue
red
brown
white

Among other things, I saw in the body of one of these animalcules a bright and round corpuscle, placed near the head, and in which a very wonderful swift motion was to be seen, consisting of an alternate extension and contraction.

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.
ANTONIE VAN LEEUWENHOEK

Freedom Man Myself Slave Stay Teaching
[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, which I notice resides in me more than in most other men.
ANTONIE VAN LEEUWENHOEK

Chiefly Crave Done Knowledge Men More Praise Pursue Time Work
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.
ANTONIE VAN LEEUWENHOEK

Equality Judgement Kind Myself Rain Togetherness Water Worm
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.
ANTONIE VAN LEEUWENHOEK

Determination Ideas Leaving Myself Reason Stubborn
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, and their bodies being transparent, that the internal motion could plainly be seen.
ANTONIE VAN LEEUWENHOEK

Animalclue Belief Body Certain Internal Land Motion Observe Quick Seen Size Transfer
For my part, I would say that the male sperm and seeds of plants have been penetrated so far that there is nothing further to discover in this great secret, but I could err in my opinion.
ANTONIE VAN LEEUWENHOEK

Biology Discover Errors Greatness Myself Opinion Plant Science Secret
In it, that sometimes more than a thousand were moving about in an amount of material the size of a grain of sand…
ANTONIE VAN LEEUWENHOEK

Amount Grain Material More Move Sand Size Sometimes Thousand
For my part, I hold it equally impossible for a small shellfish to be produced without generation as for a whale to have its origin from the mud.
ANTONIE VAN LEEUWENHOEK

Equality Hold Myself Origin Production Small
For, the circumference of one of these little Animals in water, is not so big as the thickness of a hair in a Cheese-mite.
ANTONIE VAN LEEUWENHOEK

Big Cheese Circumstance Mite One Thickness Water
The whole circumference of each of these streaks was about the thickness of a hair of one’s head. … all consisted of very small green globules joined together: and there were very many small green globules as well. [The earliest recorded observation of the common green alga Spyrogyra.]
ANTONIE VAN LEEUWENHOEK

Circumstance Consist Each Other Examining Globule Green Small Well Whole
And I imagine, that [ten hundred thousand] of these little Creatures do not equal an ordinary grain of Sand in bigness: And comparing them with a Cheese-mite (which may be seen to move with the naked eye)
ANTONIE VAN LEEUWENHOEK

Biggest Cheese Eye Grain Hundred Imagine Move Naked Ordinary Sand Thousand
The 31th of May, I perceived in the same water more of those Animals, as also some that were somewhat bigger.
ANTONIE VAN LEEUWENHOEK

Also Animal Bigger May More Perceive Same Somewhat Water
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 hand, that it consists of small round globuls driven through a Crystalline humidity or water.
ANTONIE VAN LEEUWENHOEK

Blood Drive Humidity See Talk Time Water
How little do we discover in comparison of those things which now are and forever will be hidden from our sight? The whole of which I am fully persuaded no one will ever be able to dive into, and to explain their causes and effects.
ANTONIE VAN LEEUWENHOEK

Comparison Discover Explanation Forever Hide Myself Ourselves Sight
And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof.
ANTONIE VAN LEEUWENHOEK

Anything Discovery Down Inform might People Put Remarkable
Ten hundred thousand of them could not equal the dimensions of a grain of such course Sand.
ANTONIE VAN LEEUWENHOEK

Course Dimension Equal Grainm Such Hundred Thousand Sand Ten