OF MICROSCOPIC OBJECTS. 135 



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 in the medium in shallow cells. 

 The medium advised is Mr. Far-rant's, which will be found 

 amongst those recommended. 



Many of the ZOOPHYTES which are obtained on our sea- 

 coasts are well preserved bv 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 POLYZOA, 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 Diatomacese 

 there are various 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; but if they are not thus mounted within 

 a short time after they have been gathered, about a sixth 



