52 DROPS OF WATER. 



of the body, and rotatory organs affixed to the 

 head : these, and their higher organization, render 

 them in general distinguishable from the Poly- 

 gastrica. Each of these classes is divided into 

 many families, genera, and species, the different 

 kinds amounting to nearly eight hundred well- 

 ascertained species. This number will probably 

 increase, as our microscopes are improved, and 

 observers multiply. We can understand that 

 the labours of microscopists must have been very 

 great, when we consider the extreme difficulty of 

 watching these minute productions. It fre- 

 quently happens that a specimen is lost to view 

 after only a very slight inspection, and perhaps 

 another of the same kind is not met with again 

 for days or weeks. I cannot describe the regret 



