OF MICROSCOPIC OBJECTS. 185 
following, as the best way of preserving them :—When 
caught transfer to filtered water in watch-glasses for twenty- 
four hours, in order that the contents of the laden intestine 
may be discharged. Draw off the water and add a little 
spirit of wine, which quickly destroys life. Remove all dirt 
by aid of a camel-hair pencil, and place in a few drops of 
the medium used and water (half of each) until saturation 
is complete, and then put up in the medium in shallow cells. 
The medium advised is Mr. Farrant’s, which will be found 
amongst those recommended. 
Many of the Zoopuytzs which are obtained on our sea- 
coasts are well preserved by mounting in cells, in the manner 
before mentioned, with Goadby’s fluid, or distilled water 
with one of the additions noticed amongst the preservative 
liquids. For examination by polarized light, however, they 
are usually mounted in balsam (see Chapter IV.), whilst 
those in cells present a more natural appearance as to 
position, &c., for common study. The Potyzoa, also, are 
exquisitely beautiful objects for the microscope, but require 
some little care. They should be kept in sea-water until 
their tentacula are expanded, and may then be readily killed 
by plunging in cold fresh water. Thus all their beauty will 
be preserved, and they may be then mounted in one of the 
preservative liquids. Many operators speak well of distilled 
water well shaken with a few drops of creosote, as before 
mentioned. 
As to the use of preservative liquids with the Diatemacesz 
there are varieus opinions. Some experienced microscopists 
say that there is little or no satisfaction in mounting them 
in this way. Dr. Carpenter, however, explains this differ- 
ence by his instructions as to what method should be used 
when certain ends are desired. He says: “If they can be 
obtained quite fresh, and it be desired that they should 
exhibit as closely as possible the appearance presented by 
the living plants, they should be put up in distilled water 
within cement cells; butif they are not thus mounted within 
a short time after they have been gathered, about a sixth 
