364 PRESERVATION OF MARINE ORGANISMS 



greasy nature and dries up. A mixture of vaseline 

 and beeswax is perhaps the best substance for glass 

 stoppers. It is made by first melting in a pot a few 

 small lumps of beeswax, adding some vaseline, and 

 well stirring up. The consistence of the mixture, when 

 cold, should be like soft butter on a warm day. The 

 beeswax raises the liquefying-point of vaseline. The 

 whole of the ground glass of the stopper should not 

 be coated with the mixture, but only the uppermost 

 part. Just put on a narrow band with the aid of a 

 penknife or a flat stick. 



When glass-stoppered bottles containing specimens 

 are sent by post or by train, the stoppers should be 

 tied down with string or held by a rubber band. 



Glass Jars with Metal Caps. These jars are commonly 

 sold for the storage of jam, honey, and other sub- 

 stances. Their sizes are denoted by their capacity for 

 weight, and not by fluid capacity. The most useful sizes 

 are the J pound (holding 5 fluid ounces, or 150 c.c.) 

 and the i pound (350 c.c.). The metal cap screws on 

 to the rim of the jar, and inside the cap there is a 

 thin sheet of common cork, which is quite satisfactory 

 for jam, etc., but not for fluids. The cap is sometimes 

 made of iron coated with tin or some other white 

 metal, or it may be made of a soft or hard alloy of 

 some kind or other. These jars, as purchased, are 

 very useful just for temporary purposes, but not 

 suitable for a long storage of specimens. As the jars 

 are very cheap and very convenient, several attempts 

 have been made to render them watertight and to keep 

 the fluid away from the metal. Alcohol, and especially 

 formalin, attacks the metal cap, and if left long enough 

 the metal corrodes away and the cap becomes per- 

 forated. The most successful method for making 

 these jars serviceable is the one used in the laboratory 



