Microscopical Essays, 



475 



There is a confiderable variety in it's motions ; it often turns 

 round for a long time in the fame place ; an appearance iske two 

 kidneys may fometimes be perceived in the middle of the body, 

 arid the animalculum is beautifully encompaffed with a kind of 

 halo, arifing, moil probably, from invifible and vibrating hairs. 



They are to be found in the pureft waters. 



7. Monas Tranquilla. 



Monas ovata, hyalina, margine nigro. Egg-fhaped, tranfpa- 

 rent mona, with a black margin. 



Thefe animated points feem to be nearly fixed to one fpot> 

 where they have a vacillatory motion. They are frequently fur- 

 rounded with a halo, and differ in their figure, being fometimes 

 rather fpherical, at others quadrangular. The black margin is 

 not always to be found, and fometimes one would almoft be 

 tempted to think it had a tail. It is found in urine which has 

 been kept for a time. The urine is covered, after it has remained 

 in the veflel, with a dark-coloured pellicule, in which thefe ani- 

 mals live: although the urine was preferved for feveral months, 

 no new animalcula were obferved therein. It has been already 

 fhewn, that a drop of urine is in general fatal to other animalcula, 

 yet we find that it has animated beings of a peculiar kind* appro- 

 priated to, and living in it. 



■8. Monas 



