Beck, on a Live -Trap and Parabolic Reflector. 115 
injure, even a very delicate specimen, and in some cases, when 
the object is exceedingly active, a partial stupefaction with 
chloroform is very useful. 
For a large number of small objects in water I believe this 
live-trap is peculiarly well adapted, but its use for this pur- 
pose requires a few words of explanation. I presume that 
the rapidity with w^hich small quantities of water dry up when 
under the microscope has been the annoying experience of 
all observers, and yet without limiting the amount of fluid 
there is always more or less difficulty in confining objects in 
a small space; if, however', after placing such specimens in 
this trap the free end of the glass plate be inserted in a small 
trough of water, as shown in Fig. VI, the fluid will rise by 
capillary attraction between the thin covers and the plate 
and supply every deficiency caused by evaporation. The 
water contained by the trough will last for many hours, but if 
desirable to keep the object for a longer period the slide may 
be placed up to its middle or more in a jar or bottle of suit- 
able water. With all fluid objects I have found it necessary 
to use silver instead of steel springs, as the latter rust almost 
immediately. 
