8 JOURNAL OF THE [January, 



the side of the cover-glass. The water glass may be covered, 

 to exclude any particles of dust. In this way a constant and 

 steady flow of water is secured. The over-flow is carried, by 

 means of another linen strip, from the opposite end of the 

 cover-glass into a small receptacle at the foot of the microscope. 



The following are the advantages of the apparatus : 

 ' I. A constant flow of fresh water, which may be regulated by 

 the linen strip in the siphon. The water, while running, keeps 

 saturated with oxygen, by means of the linen strip extending 

 from the mouth of the longer arm of the siphon. This strip 

 also acts as a filter, retaining any particles of dust, that may 

 have accumulated in the reservoir. 



2. The height of the capillary space between the cover-glass 

 and the slide being only of the thickness of an ordinary cover- 

 glass, all objects may easily be seen with an immersion lens. 



3. The immersion fluid may be removed from the cover-glass 

 without disturbing the objects. 



