130 THE AMERICAN MONTHLY (Jun 
rectly by rainy weather. But in view of all chances of 
error, the outlook in the direction of destroying this and 
other pests with artificially grown parasites does not 
seem to me discouraging.—Ky. Ag. Hap. Sta. 
\ Simple Form of Monochromatic Illuminator for 
the Microscope. | 
ARTHUR M. EDWARDS, M.D., F.L.S. 
For a long time, I have used a simple form of mono- 
chromatic illuminator, and it seems to answer perfectly. 
It can be employed for casting a colored light of one tint 
be it large or small. A whole room can thus be tinted 
any color it is desired to get, and, of course, it answers 
for use in the microscope. It may be described as giv- 
ing a pure blue color, for that is the tint that it is most 
desirable to obtain. A vial is taken which has flat sides. 
Such an one is extremely common and is used by drug- 
gists everywhere. The sizeis not important but when 
used for the microscope, a small one (say of about two 
ounces capacity) will answer. - When employed for illu- 
mination of larger objects, a larger one will be neces- 
sary, but a pint size is quite big enough. 
This bottle is filled with water which has aniline blue 
dissolved in it. These are numerous but any of them will 
do for they transmit the right blue colors. When it is 
used, it is put between the source of light (sunlight or 
lamplight or gas flame), and the microscope so that the 
light through it can fall only on the: object, be that con- 
centrated by meansof a mirror, or lens or falling simply 
on the slides. It is extraordinary how pure the light 
seems when thus viewed. The most difficult object, as 
Hyalodiscus subtilis or even Suriella gemma seems to 
start out when thus viewed, and the markings seem to 
be easy to resolve. In fact, we find that any other color 
than blue seems to be glaring, and we always turn to it 
