IMBEDDING METHODS. 



93 



FIG. 3. 



smears the glass plate with glycerin, then arranges 



metal " squares," and then fills the box with collodion, which 



is poured out again immediately. As 



the ether evaporates, a thin layer of 



collodion remains behind, which suffices 



to keep the paraffin from running out. 



Even without the collodion, the mere 



cooling of the paraffin by the metal 



will generally suffice to keep it in long 



enough for orientation, if it is not in a 



superheated state when it is poured in. 



In such a collodionised box the 

 paraffin may be kept in a liquid state 

 by warming now and then over a spirit 

 lamp, and small objects be placed in 

 any desired position under the micro- 

 scope (Journ. Roy. Mic. Soc. [N.S.], 

 ii, p. 880). 



A lighter form of " squares/' made of brass, and devised 

 by ANDRES, G-IESBRECHT, and MAYEE, is described loc. cit. (see 

 Journ. Roy. Mic. Soc., 1883, p. 913). 



FRANKL (Zeit. f. wiss. Mile., xiii, 1897, p. 438) builds up 

 boxes with rectangular blocks of glass, which may be found 

 convenient, but are more expensive than the metal squares. 



SELENKA has described and figured another sort of appa- 

 ratus having the same object. It consists of a glass tube, 

 through which a stream of warm water may be passed and 

 changed for cold as desired, the object being placed in a 

 depression in the middle of the tube (see Zool. Anz., 1885, 

 p. 419). A simple modification of this apparatus, which 

 anyone may make for himself, is described by ANDREWS in 

 Amer. Natural., 1887, p. 101 ; cf. Zeit. f. wiss. Mik., iv, 3, 

 1887, p. 375; or Journ. Roy. Mic. Soc., 1887, p. 510; and a 

 more complicated imbedding and orienting box, seldom 

 necessary, is described by JORDAN, in Zeit. f. wiss. Mik., xvi, 

 1, 1899, p. 32 ; Journ. Roy. Mic. Soc., 132, 1899, p. 549. 



For small paraffin objects the following procedure is very 

 useful. The object is removed from the melted paraffin, 

 the superfluous paraffin is removed by means of blotting- 

 paper, and the object placed on a cylinder of paraffin. A 

 piece of stout iron wire is now heated in the flame of a 



