ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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easily into a sleeve which is carried on the movable arm D, this being 
fixed, with the object-clips, to the ebonite hand-frame H. 
Knife-Holder for Microtomes.* — Dr. R. Hesse describes a knife- 
holder (fig. 42), with which it is possible to vary the inclination of the 
knife from the horizontal position. The sliding arc has a radius of 
15 cm. The graduations at the side are millimetres, 1 mm. correspond- 
ing to a movement of O’ 8° of the knife. The holder is made by 
R. Jung, of Heidelberg. 
Fig. 42. 
(4) Photomicrography. 
Systematic Photomicrography.^ — Mr. J. B. Shearer points out that 
the time of exposures, &c., in photomicrography depends too often on 
guess-work, and suggests a systematic keeping of records of exposures 
which have been successful, in order to serve as a guide in future cases 
where the conditions are more or less similar. For this purpose he has 
had printed a book of forms to be filled in with the details as to lenses 
used, distances of the light and photographic plate, time of exposure, 
colour of object, &c. 
The apparatus used by the author consists of a turntable L (fig. 43) 
carrying the Microscope, Welsbach lamp, and bull’s-eye condenser. After 
the light, &c., has been arranged, the turntable is swung round, and the 
Microscope-tube is inserted in the camera front. The image is focused 
from the back of the camera by a rod D, which passes the whole length 
of the camera-bed and actuates a band passing over the fine adjustment 
of the Microscope. For the illumination of opaque objects, the lamp 
can be moved with respect to the Microscope. An arrangement, in 
* Zeitsclir. f. wiss. Mikr., xiv. (1897) pp. 13-5 (1 fig.), 
f Trans. Amer. Micr. Soc., xviii. (1897) pp. 117-130 (5 pis.). 
