ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 131 



into it is cemented a small cover circle ; round the central aperture 

 is turned concentrically a deep groove to form an air-space, and into 

 which a moistening thread can be placed if required. A brass cap 

 with milled edge and central aperture has cemented to the inside, over 

 the aperture, a thin circle cover, and on this the object is to be placed. 

 Over the outside of the circular ebonite block is slipped a thin, narrow 

 indiarubber ring ; the brass cap must fit correctly over the ebonite 

 block, the ring of the cap closing upon the indiarubber ring, making 

 the whole air-tight, and bringing the free surface of the droplet of 

 liquid to touch the surface of the small glass circle, in a similar way 

 to the ordinary live-box. The brass ring warm stage is now placed over 

 the circular block of ebonite. In this way it is found, if care be taken, 

 that the circular thermometer placed on the thin cover indicates 

 90° Fahr. without the water boiling, and if protected from cooling by 

 cloth above and below, the temperature can be equably maintained. 



Another plan is to employ two thin ebonite plates 3 by IJ in., 

 pierced with apertures about 5-8ths in. bevelled on one side ; each is 

 closed with a thin cover circle, one is used as the base-plate, the 

 other as an ordinary slide. The object is put on the cover ; upon 

 this is gently placed a very thin cover-glass about 7-16ths in. in 

 diameter ; one or two small indiarubber bands are placed flat on the 

 lower plate, the upper one is reversed over them, and the two are 

 bound together by two indiarubber rings. An air-tight space is thus 

 easily made, and if it be desired to add moisture, a thin circle of damp 

 blotting-paper can be placed within the rings, or if between them, the 

 edge of the ring of paper may project and be moistened as required ; 

 but the pressure from the bands must not be too great. If increased 

 temperature be required, the whole can be put on the brass ring stage 

 without trouble. 



Dr. Maddox does not claim that there is much novelty in these 

 different forms, but he believes they differ somewhat from any de- 

 scribed, and may prove useful in the study of minute organisms, 

 which has so largely developed within the last few years. 



Dibdin's Hot Stage.*— Mr. W. J. Dibdin also describes a form of 

 " Hot Stage " in which simplicity is probably carried to its furthest 

 limit. It consists only of a square white glass bottle resting on the 

 stage (which must be inclined 45°). In its cork is a thermometer 

 and two siphon tubes, one serving as a waste-pipe and the other 

 communicating (by a piece of indiarubber tubing) with another 

 siphon-tube in the cork of a flask, which is kept heated on a tripod 

 over a spirit-lamp, and also has a thermometer. A constant stream 

 of water is thus kept flowing through the bottle on the upper side of 

 which the object is placed. Mr. Dibdin used the apparatus for 

 observing the bursting-point of starch cells. 



_ Caton's Fish-trough. — This (fig. 26) consists of an oblong or 

 slightly conical box of ebonite, closed at one end and large enough to 

 hold the body of a minnow or stickleback very loosely. This box is 

 attached to a plate of ebonite, which can be placed on the stage of the 



* Journ. Post. Micr. Soc, i. (1882) pp. 177-8 (1 fig.). 



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