DROP I. 



I HAVE mentioned in the introductory chapter, 

 that many of the microscopic objects found in 

 water are at present not sufficiently known, to 

 enable naturalists to determine, beyond dispute, 

 whether they belong to the animal or vegetable 

 kingdom. Ehrenberg thinks, to the former be- 

 long all the genera I am about to describe in this 

 section. Dr. Meyen is of opinion that many of 

 these are decidedly vegetable ; and others imagine 

 that all may belong to the latter kingdom. By 



