ZOOLOGY AND BOTANY, MIOBOSOOPY, ETO. 327 



cover, which is the object-carrier, on the glass stage over the aperture, 

 it is cemented on a rather deep ring, made by cutting off a glass tube 

 of a diameter equal to that of the aperture. The ring may then be 

 cemented to the stage, or simply made to rest in place upon it. It 

 will be seen that the bibulous paper stage may now be made to fit 

 close up to the ring, as the object-carrier is lifted above it into the 

 cell or moist chamber formed by the outer glass tube and its thin 

 rubber cover. The ring carrying the object plate and the stage 

 perforation must be large enough to admit the substage condenser. 



The author has also applied the principle of the above to the 

 construction of a moist chamber which he has in constant use, and 

 finds handy. An ordinary glass slip is taken ; a ring with a cover- 

 glass cemented on the top rests at its centre ; then a number of 

 layers of blotting-paper of proper size, with the centres cut out, are 

 placed upon the slide sufficient to reach above the object ; the lower 

 paper should fit close up to the ring, and have a tongue on one 

 side. After the object is in place, and covered or not, as the case 

 may be, a slide is put over all, and the combination is put over a 

 dish of water, with the tongue of bibulous paper reaching into it. 

 The drop will not evaporate, and being surrounded by a quantity of 

 air, the infusorian or rotifer under observation will keep in good 

 health for a long time. A special slide and cover, 3 X li in., 

 are rather more convenient, giving a larger cell than ordinary slips. 



A still better plan is to use two brass plates, 3 x 1^ in., instead 

 of glass. The lower one is perforated at its centre, and the ring 

 and object-carrier cemented over it ; the tongued bibulous paper is 

 then put on as before (only one layer is required to supply moisture, 

 but an additional one with a larger hole at the centre facilitates the 

 removal of the cover). The other plate should have a larger central 

 perforation, over which a ring and cover-glass are cemented. When 

 in use this one is placed over the former, covering the object with 

 the cell, and the whole placed over a dish of water, with the tongue 

 reaching the water. It will be seen that examination with a low 

 power may be made at any time through the cover — the cover to be 

 removed for the use of high powers. 



Klonne and Miiller's Bacteria-finder. — In the description of this 

 apparatus (ante, p. 127) more stress should have been laid on the fact 

 that the upper part of the frame is level with the top of the stage, so 

 that the slide moves on the surface of the stage itself, thus allowing 

 the Abbe condenser to be brought close to the under side of the slide, 

 an advantage which is not obtainable with the earlier forms by 

 Schmidt and Hansch.* 



Dr. W. Behrens suggests j the addition of a vernier for reading 

 the scale on the circular slot, which it is now difficult to do on account 

 of the end of the movable frame by which it has to be read throwing 

 a shadow on the scale, and points out the inconvenient extent to 

 which the apparatus projects behind the Microscope. The makers 



* See this Journal, iii. (1880) p. 878. 



t Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 502-7 (2 figs,). 



