45§ Microscopical Essays, 



fometimes obliquely, fometimes ftrait forwards, at other times 

 circularly, one while rolling and turning round, and then running 

 backwards and forwards through the whole dimenfions of the 

 drop, as if in fport ; at other times attacking with avidity the 

 little heaps of matter they meet with in their way. They know 

 how to avoid with dexterity any obftacles that would interrupt 

 their motion, and even to avoid one another ; you may fee hun- 

 dreds in motion in a drop of water, that never ftrike againfl each 

 other ; fometimes they will fuddenly change the direction in 

 which they are moving, and take one diametrically op polite 

 thereto. By inclining the glafs on which the drop of water is 

 laid, it may be made to move in any direction ; the animaicula 

 in the drop will fwim as eafily again!!, the fiream as with it, 



If the water begins to evaporate, and the drop to grow fmaller, 

 they flock impetuoufly towards the remaining fluid ; an anxious 

 defire of attaining this momentary refpite of life is very vifible, as 

 well as an uncommon agitation of the organs by which they im- 

 bibe the water. Thefe motions grow languid as the water fails, 

 till they at laft ceafe. If they are left dry for a little time, it is im- 

 poflible to re-animate them by giving them frefh water. 



Animaicula and infects will fupport a great degree of cold, but 

 both one and the other perifh when it is carried beyond a certain 

 point. The fame degree of heat that deftroys the exiftence of 

 infecls, is fatal to animaicula ; as there are animaicula produced 

 in water at the freezing point, fo there are infecls which live in 

 mow. 



