176 PHILOSOPHICAL TRANSACTIONS. [aNNO 1705. 



ABG represents the case or sheath, into which the animalculam withdraws, 

 on the least shaking or stirring of the weed, and then thrusts out again, as far 

 as BCPG, and at the same time appear the two little wheels represented by 

 CDEP ; in observing the motion of which, one would be apt to think they were 

 two real revolving wheels. But soon as we could place the animalculam* before 

 our eyes, in such a position as to view the little wheels, not partially, as is here 

 represented, but completely, and all at once, we were convinced of our mistake 

 in our former assertions; for now we saw clearly, that what appeared before to 

 be two distinct little wheels, was really one and the same circumvolution. 



Fig. 28 represents the said wheels, larger than they really appeared, in which 

 the rotation proceeds from h to i, and so on from i to k, and from k to l and 

 M. I was at last fully satisfied about this surprising and regular phenomenon ; 

 for having thrown away the weeds, to whose roots the animalcula adhered, 

 and made my observations on several others, I found the same appearance 

 every time, only with this difference, that the internal arches in the said fig. 

 at K and m, were not near so much indented. 



During those observations, one animalculum appeared as in fig. 29, n being 

 that part of it by which it was fastened to the weed. This animalculum liad 

 his receptacle or little house, represented by not, composed of round bubbles, 

 which figure had not occurred to me before. When this animalculum had 

 thrust that part of its body, from o to p, out of its case or shell, it extruded 

 at the same time that surprising wheel-work which consisted of four round 

 parts, represented by pqrs, three of which were to be seen very plain, but the 

 fourth at t was almost hid from the sight. This wheel-work moved from v 

 to a, and from r to s. 



Fig. 30 represents that instrument, which in fig. 28, is for the most part 

 described by pqrs, much larger than it really appeared ; in which we saw the 

 said teeth and wheel-work move from arc to d, and from d to efg, and in 

 that manner perform its whole revolution ; and at the least sudden touch of the 

 animalculum, it presently drew the wheel-work into its body, and then its 

 whole body into its case or shell, so that we could see nothing but a kind of 

 horn, as not, fig. 29, in which it hid itself; but it quickly put forth that part 

 of its body represented by opaRST, and then the rotation or wheel-work pro- 

 ceeded as before. 



If any one should be inclined to make this experiment, he must take care to 

 choose out duck-weeds that have long roots ; for I never observed any of these 

 animalcula in the short roots of young weeds, nor indeed in the great roots, 



* These aoimalcules belong to the LinnaBan genus vorticella. 



