SELECTION, ETC., OF OBJECTS FOR PHOTOGRAPHING. 97 
For preserving a pure culture of any particular 
species, the culture-flask and method of manipu- 
lation described by the writer in his paper already 
referred to, is recommended. 
The thin glass cover, with the stained Bacteria 
attached, is mounted upon a slide by means of a 
circle of white-zinc cement, made upon a turn- 
table. The shallow cell made by this circle of 
cement is filled with camphor-water, weak carbolic- 
acid water, or simply distilled water. 
Great care will have to be exercised in the 
selection of a field, and in focusing, in order to 
obtain a satisfactory picture. 
Am@p&. (PuateE II. Fia. 1.) 
Especial attention is called to the photo-micro- 
graph of an amoeba (Plate II. Fig. 1),’ as it is 
a photograph from life of this interesting and 
much-talked-of creature, and because it illustrates 
the fact that transparent objects are the best 
suited for photography, inasmuch as they alone 
show interior details of structure in a satisfactory 
manner. 
The interior details seen in this case, however, 
are not details of structure, except perhaps the 
cavity just above the dark-colored sphere, which 
is a vacuole. The sphere, which might be mis- 
taken for a nucleus, is a unicellular alga of a 
bright red color (winter form of Protococcus, or so- 
called Hematococcus), and was taken in by the 
1 An accident to the negative has made it necessary to substi- 
tute another and inferior photo-micrograph of Amceba for the one 
described in the text. ° 
