OF ANIMALCULES. 31 



rating, — a circumstance which distinguishes them from 

 the grape monad. 



They are found in most waters containing vegetable 

 matter, and even in sea- water that has been kept some 

 time ; but are not so numerous in the latter. A mag- 

 nifying powder of from 350 to 500 is sufficient. 



3. Mo^ AS punctiwi (Bobo punctU7Ji , £.) The pointed 

 Monad. — These animalcules are slightly noticed byEhren- 

 berg. They appear as mere dark points, unless seen 

 under a good deep power and proper illumination, when 

 they assume the form of short inflexible cylinders : they 

 are generally found in clusters, and if the microscope 

 be very perfect, a delicate slender filament, or tail, 

 may be seen attached to the middle of each, similar 

 to the filaments or stalks of the common bell polype, 

 but more minute : by the occasional contraction of these 

 filaments the animalcules move by sudden starts, and 

 when several contract simultaneously they appear like 

 scintillations, and have a pretty effect under the micro- 

 scope, not unlike some kind of fire- works. 



The engraving. Fig. 3, represents a group of them, 

 highly magnified; the filaments are not shewn. 



They are found in various vegetable infusions ; are 

 very abundant about the infused stalks of the spider- wort, 

 Tradescantia Virginia ; and are best seen by lamp-light, 

 under a power of 500 to 600 times. 



Ehrenberg has added three other species to the genus 

 BoDo, (for their generic characters, see Book III. :) 



