18 



Transactions of the Society. 



or linen ring is cut with two projecting pieces, one on each side, 

 these passing into two little wells sunk into each end of the tank, 

 so that the paper or linen can he kept constantly and evenly wet, 

 and thus air entering the chamber can only do so by passing 

 through the saturated material between the flanges. 



Mr. C. Lees dirties has kindly consented to exhibit and explain 

 a box constructed by his firm to my specification. 



Fig. 1. 



A. Cover-glass carrier. 



D. Cover-glass. 



F. Reservoirs. 



H. Outlet for warm water. 



B. Filter-paper, blotting-paper, or linen. 



E. Glass tablet. 



< i. Inlet for warm water. 



I. Opening for thermometer. 



To sum up, the chief points and advantages of the contrivance 

 are: — ■ 



1. A minute living monad or bacillus can be kept under 

 continuous observation with a } \j oil-immersion objective and 

 critical illumination for an indefinite period. 



2. The oil may be wiped off from the cover and a dry lens sub- 

 stituted without disturbing the living specimens under observation. 



