ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
785 
plate-glass out and ground on the surfaces, to rest on one half of the 
table for the purpose of evaporation in mounting diatoms, a more uniform 
Fig. 111. 
distribution of the heat being thus obtained as well as absorption for 
any particle of water which may overflow the cover-glass.” 
(4) Photomicrography. 
Photography as an Instrument for recording the Macroscopic 
Characters of Micro-organisms in Artificial Cultures.* — Prof. G. F. 
Atkinson recommends the following mode of proceeding for this purpose. 
By cutting off the perpendicular rays of light, and throwing oblique rays 
from several directions through the plate-culture upon the sensitive 
plate, the colonies are differentiated strongly in all their exquisite forms 
and tracings. The culture plates (Petrie dishes) or tubes are inserted 
in an opening in the end of a box, which is painted perfectly black on 
the inside. Sliding boards in a grooved frame, each cut to clamp over 
half the Petrie dish, and lined with black velvety stuff, hold the plate- 
culture in position. The lens of the camera is pointed towards a window 
with the plate-culture between them. A perfectly black screen 30-40 cm. 
in diameter is then hung upon the window directly in front of the object, 
in order to cut off the perpendicular rays of light. 
* Bull. Torrcy Bot. Club, xx. (1893) pp. 357-8. 
