VOL. XXIV.] PHILOSOPHICAL TRANSACTIONS. 177 



when once they are covered with a rough matter, and tend to decay, as I have 

 seen a great many in the beginning of August; and he ought not to leave off 

 his inquiry, though he should meet with 10 or 20 roots that have none of 

 the abovementioned animalcula in them ; for I have sometimes examined more 

 than 2b roots, without meeting with any of these animalcula on them ; as also, 

 on the contrary, I have sometimes found three of them on one weed. 



I was the more easily induced to assert what I formerly did, about the ani- 

 malcula that are fastened to the roots of duck weed ; viz. that they had two 

 distinct revolving wheels ; because I had discovered several animalcula that pro- 

 truded two wheels out of the forepart of their body, as they swim or go on 

 the sides of the glass; one of which is represented by fig. 31. This sort of 

 animalcula I found in great numbers in the gutter-water in summer, which had 

 stagnated some days in the small pits or cavities of the lead. These animalcula 

 are gradually less and less, so that 50 small ones are not so large as one great 

 one, or full grown animalculum, big with young. 



In October 1702, I caused the dirt of the gutters, when quite dry, to be 

 gathered together, and taking a small quantity of it, I put it into a paper on 

 my desk; since which time, I have often taken a little of it, and poured on 

 it boiled water, after it had stood till it was cold, that I might obviate any ob- 

 jection that should be made, as if there were living creatures in that water. 

 These animalcula, when the water runs ofF, or dries away, contract their bodies 

 into a globular or oval figure. After the said dry substance had lain near 21 

 months in the paper, I put into a glass tube of an inch diameter the remainder 

 of what I had by me, and poured on it boiled rain water, after it was almost 

 cold; and then immediately viewed the smallest parts of it, particularly that 

 which subsided leisurely to the bottom, and observed a great many round par- 

 ticles, most of which were reddish, and were certainly animalcula; some hours 

 after I discovered a few that had opened or unfolded their bodies, swimming 

 through the water, and a great many others that had not unfolded themselves 

 were sunk to the bottom, some of which had littleholes in their bodies; from 

 whence I concluded, that the little creature called the mite had been in the 

 paper, and preyed on the said animalcula. Next day I saw three particular 

 animalcula swimming through the water, the smallest of which was 100 times 

 smaller than the above said animalcula. So that it is surprising that these small 

 insects can lie 21 months dry, and yet live; and as soon as ever they are put 

 into water begin to swim, or fasten the hinder parts of their bodies to the glass, 

 and then protrude their wheels, as in the figure, just as if they had never 

 wanted water. 



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