44 PHILOSOPHICAL TRANSACTIONS. [aNNO 1713. 



If we observe those animalcala, which, with their long tails, are fastened to 

 some part of the weed, as we have discovered a great many on the small roots 

 of the duck-weed ; we may observe, that they do not only make a circular 

 motion with the extreme part of their bodies, which motion, in proportion to 

 the said part, is very great; but they can likewise draw in their tail, and that 

 with a very quick motion; by which means they can move the water out of its 

 place, when they stretch their tails out again, and so bringing fresh water under 

 them, they procure new food. 



I likewise observed a very few animalcula, whose bodies were short and thick, 

 and much larger than those other animalcula that lodged themselves in a sheath, 

 and were fastened by their tail, or extreme parts, to the little roots of the duck- 

 weed: and though these short and thick animalcula could move from place to 

 place, yet they also had a circular motion in the fore part of their bodies. From 

 whence I concluded, that those motions served some other purposes than only 

 to draw their food to them. On further considering what could be the use of 

 these indented wheel-works, which are so like the indented wheels of a clock, 

 or watch, I must own that they are very necessary to produce a great motion 

 in the water ; for, were it a round and smooth wheel, it would cause but a very 

 small motion; whereas now, each tooth in the said wheel or circle produces a 

 great motion, in comparison of what a smooth and plain wheel would do. 

 Whence appears the surprising order in the formation of such small creatures, 

 which are not to be perceived by the naked eye. 



In the beginning of August being in a garden that had a pond full of fish, 

 on the water of which I observed floating a thin scum, of a greenish colour, 

 though there was nothing green in the water; which seemed strange, because 

 at other times I had observed that the water of the pond was very clear, as 

 well as the stream which fed it ; and I was told that when it rained, the said 

 scum disappeared. I took a little piece of a wooden lath, and drawing it over 

 the superficies of the water, I placed a small drop of the water on a green wine 

 glass, and viewing the same with the microscope, I discovered an inexpressible 

 number of animalcula, so exceedingly small, that they almost escaped my sight 

 through the microscope : there were also several sorts of larger animalcula, 

 mixed with a great number of little air bubbles, of an exceeding smallness. 



I cannot forbear acquainting you, that I have lately observed in the flesh of 

 a whale, and the same is to be said of an ox, and even down to a mouse, 

 that its fibres, though l6 times smaller than a hair of my beard, yet are sur- 

 rounded or involved in little membranes, in such manner, that the fleshy par- 

 ticles do not touch each other. 



