OF ANIMALCULES. 33 



able, being sometimes in the middle, sometimes a little 

 towards the fore part, at others nearer the posterior. 



The appearance of two kidney-shaped bodies may 

 sometimes be perceived in its centre, and the body 

 is beautifully encompassed with a halo, arising, probably, 

 from fine ciliee or hairs. 



It moves in a variety of ways, and often revolves with- 

 out changing its situation. Group 5 represents this 

 animalcule magnified : its real size is about 1- 1440th of 

 an inch. It is readily seen with a power of 300. 



They are found during the summer in clear soft water. 



9. MoNAS tranquilla. The slaiionari/ Monad, — Egg- 

 shaped, transparent, with a black margin. 



10. MoNAS lamellula. The laminated, or plate-shaped 

 Monad, is of a white colour, twice as long as its 

 breadth, very transparent, with a dark margin ; it often 

 appears as if it w^ere double. Its motions resemble vi- 

 brations. They are mostly found in salt water. 



11. MoNAS pulvisculus. The dust Monad. — Transpa- 

 rent animalcules, with a green margin. When magnified, 

 they appear like small pellucid grains of a spherical form. 

 Their circumference is green. They sometimes swim 

 in company, but are not connected like the grape monad : 

 this it is necessary to remark, as they are about the 

 same size, and might therefore be mistaken for them. 

 Ehrenberg has not observed them in clusters, but has 

 distinctly discerned their mouths, which are furnished 

 with from ten to twenty cilias, or hairs. A line of a dark 

 green colour may be observed in some specimens across 



