Microscopical Essays. 



441 



thing very much refembling the little wheels of a mill, moving 

 with great velocity, may be difcovered on both fides of the edges 

 of this anterior part. 



Thefe vorticellae are able to contract themfelves fuddenly. 

 They may be made to do this, either by touching them, or 

 moving the fubftance to which they are affixed. When they con- 

 tract, the edges of the anterior parts are drawn quite into the 

 body ; on refuming their former pofture, the edges may be feen to 

 come forth, and put themfelves in motion as before. Minute 

 fub fiances that float in the water are often forced down into thefe 

 openings, and fome times are thrown out again. 



They are capable of fwimming about fingly, but their form is in 

 that cafe confiderably different from that which they have when 

 they are fixed. To fee regularly in what manner the clutters are 

 formed, and in what way thefe little creatures multiply, it is beft 

 to obferve one that is fixed by itfelf. 



The pedicle of a fmgle vorticella is at firft thort, but it foon 

 grows longer, and then begins to multiply, that is, to divide, or 

 fplit itfelf in two lengthways. To effecl this, the lips are firft 

 drawn into the body, the anterior part clofes and becomes round, 

 and lofes it's bell fhape, the motion about the lips ceafes, though 

 a fmall degree of motion may be perceived within the body. 

 The anterior end flattens gradually, and fpreads wider in pro- 

 portion as it grows fmaller. It then gradually Tplits down the 

 middle, that is, from the middle of the head to the pedicle, fo 

 that in a little time two feparate round bodies appear to be joined 

 to the end of the pedicle, that before fupported but one. 



3H The 



