PREFACE. 



HAVING for several years derived great and in- 

 creasing pleasure from the use of a good micro- 

 scope, particularly in the investigation of the 

 minute creatures contained in water, and wishing 

 to extend this pleasure to others, I venture to 

 make public the following pages ; for though 

 there are several learned works already on the 

 subject, my experience and observations may be 



