214 LEEUWENHOEK AND HIS “LITTLE ANIMALS” 
Two days after the foregoing discoveries, I again beheld 
the small parcel of water aforesaid in the glass tube; and 
as I did so, I saw a huge number of extreme small fishes, 
or animalcules, which I may call little eels,’ because in 
swimming forwards they lashed their bodies like eels 
do, and so quick that ’twas marvellous. These little fish 
did mostly stay close beside one another, and round the 
circumference of the tube, and in vast numbers; and in 
my judgement their length was equal to the diameter 
of one of those blood-globules which make the blood red. 
And they remained alive some seven days, after which 
time I could make out only one every now and then. 
Among these little animals, or little fishes, I did also 
see a-Swimming a few smaller animalcules, whereof I 
deemed that eight of ’em together were no bigger than 
the said blood-corpuscle*: and now I could no longer 
discern that little structure that I heretofore likened to a 
little branching vein, how oft soever I looked for it. 
These last-mentioned animalcules were so prodigiously 
increased in two or three days, that ‘tis incredible ; though 
by now half the water was evaporated away. 
All the water that I have so far spoken of, which I had 
put in the glass tube, and wherein the foresaid multi- 
plicity of little animalcules were bred, I deemed (to the 
best of my knowledge) to be no more in bulk than the 
eighth part of a green pea; but not being content with 
this my estimate, I went and weighed a like quantity of 
water, and I found its weight two grains. I did also 
weigh some peas, and found that a common pea weigheth 
eight grains. 
Through the microscope with which I had carried out 
the first observations, I imagined I still saw,* in water 
* Probably Spirilla—certainly bacteria of some sort. 
* i.e., their diameter was about half that of a red blood-corpuscle. 
Undoubtedly bacteria. 
° L., it will be recalled, commonly used a different microscope for each 
separate observation—the object being more or less permanently fixed and 
focussed before the lens. 
