Robert Hooke finally succeeded in replicating Leeuwenhoek's observations of little animals

November 25, 1677

Robert Hooke finally succeeded. Afer the pepper had steeped in the rainwater for nine or ten days, he was able to show "great numbers of exceedingly small animals swimming to and fro. ... so that there was no longer any doubt of Mr. Leewenhoeck's discovery. ... there could be no fallacy."


Birch's History, vol III, p 352, 15 November 1677 (O.S.) in London:

The first experiment there exhibited was the pepper-water, which had been made with rain-water and a small quantity of common black pepper put whole into it about nine or ten days before. In this Mr. HOOKE had all the week discovered great numbers of exceedingly small animals swimming to and fro. They appeared of the bigness of a mite through a glass, that magnified about an hundred thousand times in bulk; and consequently it was judged, that they were near an hundred thousand times less than a mite. Their shape was to appearance like a very small clear bubble of an oval or egg form; and the biggest end of this egg-like bubble moved foremost. They were observed to have all manner of motions to and fro in the water; and by all, who saw them, they were verily believed to be animals; and that there could be no fallacy in the appearance.

They were seen by Mr. HENSHAW, Sir CHRISTOPHER WREN, Sir JOHN HOSKYNS, Sir JONAS MOORE, Dr. MAPLETOFT, Mr. HILL, Dr. CROUNE, Dr. GREW, Mr. AUBREY, and divers others; so that there was no longer any doubt of Mr. LEEWENHOECK'S discovery. Notice was ordered to be taken of this discovery, and further trial was desired to be made upon rain-water alone; and upon rain-water, in which had been steeped, wheat, barley, and other seeds and grains: as also that blood and several other liquors should be after the same manner examined. The shape of the microscope and the manner of examining the --

[ Birch/Hooke break off ]

The following is missing from Birch's History. However, it is in Hooke's recently discovered hand-written folio, The Hooke Folio Online, CELL/RS/HF_111.

The image below is the folio page from the minutes for that November 15, 1677, meeting that Hooke took as the Society's secretary. The transcription below was copy-edited by me for clarity.

-- liquor was as follows. First the pipes were drawn exceeding thin and pretty small, too, with about the bigness of a pig's bristle: these by the microscope were magnified into a cylindrical pipe of 3 inches in diameter that appeared at least 100 times bigger in diameter than really it was and consequently all things that appeared in it were proportionally magnified.

These pipes dipped into the pepper water were immediately filled with the liquor readily ascending up into them. These pipes were stuck with wax upon a brass plate perforated through the middle so as to let the light through. The plate was made to slide on a small piece of brass so as to be set along but differed from that object glass, there being looked upon against the flame of a candle, not directly but with a glancing light. The small insects appeared swimming to & fro with various motion like very small clear shining bubbles.

After this experiment, much debate arose whether these were produced by the pepper or by the water, whether from equivocal or seminal generation. Mr. HENSHAW, Sir CHRISTOPHER WREN, and Dr. HOLDER were of opinion they were equivocal. But HOOKE and others that they were of seminal productions, that twas possible they were from eggs dispersed in the air and so brought down by the rain or sticking on the pepper before it was steeped.

Upon this, Sir CHRISTOPHER WREN suggested that trial of that might be made by baking the pepper. For it was probable if there were such eggs their prolific faculty would be destroyed.

Mr. HENSHAW supposed it was from the heat of the pepper and the fermentation of the said tincture that they were produced and not from seed, and urged that such equivocal generations were observed in the hairs of stone horses tails steeped in water, producing a kind of snake. It was doubted by many whether that creature (which was generally from its shape supposed to be so generated) were not some distinct species of living creature and there was no one present that (though most had seen them) that could positively affirm that they had known them so generated.

Mr. HENSHAW related and affirmed that twas not only this substance that was capable of animation but that lute string or gut strings would by being steeped in water do the same thing.

Equivocal generation held that individual animals came from unrelated host organisms.