Of Animalcules in Fluids. 1.21 
theii 4 tail into a fcrew-like form, as at b, fig. 206„ 
and this fpring is fo flrong, that when the tail is entan¬ 
gled, as it frequently is by the extremity, they bring back 
their whole bodies by the jerk and convolution of the 
tail, which quickly returns to its firft ffraitnefs. When 
they lie ftill, they thruft out and pull back again a 
bearded tongue, and a current conftantly runs towards 
them, occafioned probably by the motions of fome fins 
or legs too fine to be difcerned. 
Thofe animalcula exhibited by fig. 207. abound in all 
Waters, and are largeft of all; their length is about an 
hair’s breadth, and three or four times more than their 
own k ; they are very thin and tranfparent, and turn 
themfelves very quick, fhewing both back and belly; 
their edges are adorn’d with a great number of minute 
feet feen chiefly at the two extremities; at one end there 
is a kind of brufh refembling a tail; they are fwift in 
motion, and by their turns, returns, and fudden hops, 
feem to be continually hunting for prey, a reprefents 
one of them on its back; b one on its belly ; at c and d, 
is feen how they often appear in other pofitions. 
There is generally another fort of an. oval fhape, as at 
fig. 20S. a b c, lengthening and fhortening themfelves as 
occafion requires, and fometimes two of them may be 
feen conjoined, as at a. 
Another fort are a kind of capillary eels, they wave 
their bodies but little, move equably and flow, and fvvim 
as well backwards as forwards. See fig. 209. 
Several kinds of mixtures put amongft them, while 
they are before the microfqope, produce different effects.. 
The fmallefi: drop of fpirit of vitriol, upon the point of 
a pin, being put to them, they immediately tumble down 
dead; diffpiyed faits kill them ; but with this difference, 
K 2 inftead 
k Phil. Tranf, No 284, 
