98 PHOTO-MICROGRAPHS. 
creature at its last meal, which it was quietly 
digesting while sitting for its photograph. The 
granular material seen about this colored sphere 
is the partially digested remnant of former meals. 
The outline of the jelly-like mass, which is flat- 
tened out against the glass cover, is very distinctly 
seen, and below has a wavy appearance. On the 
left is a small object out of focus, probably a starch- 
grain, in contact with the amceba. 
Transparent objects which have a different refractive 
audex from that of the medium in which they are placed, 
do not usually requre to be stained; for the in- 
creased photographic contrast which is obtained 
by staining destroys the natural appearance, and 
the picture no longer conveys the idea that the 
object is transparent. It is consequently brought 
nearer to the level of a woodcut, and, to a certain 
extent, loses its value as a photo-micrograph. 
Ameebse are found in ponds and ditches, and 
are commonly attached to the surface of decaying 
leaves, water plants, etc. 
UNICELLULAR ALGA. 
The unicellular Algz should be mounted for 
photography in very shallow cells, made by turn- 
ing a circle of white-zinec cement upon a slide. 
Their color and natural appearance will be pre- 
served in an aqueous medium, such as weak 
carbolic-acid water or camphor water. Unfortu- 
nately, photography cannot reproduce the rich 
ruby color of Protococcus mvalis, or the bright 
green of Protococcus viridis. The deeply colored 
